diff --git a/20210107/bsort-1.c b/20210107/bsort-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..3c02adc72e6a7e702e2c7c68c838fc94cc8ef547
--- /dev/null
+++ b/20210107/bsort-1.c
@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+ display (name, left, right);
+ usleep (200000);
+ return result;
+}
+
+void sort (char **name)
+{
+ for (int i = 1; name[i]; i++)
+ if (compare (name, i - 1, i) > 0)
+ {
+ char *temp = name[i - 1];
+ name[i - 1] = name[i];
+ name[i] = temp;
+ }
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ sort (name);
+ display (name, -1, -1);
+ return 0;
+}
diff --git a/20210107/bsort-1a.c b/20210107/bsort-1a.c
new file mode 100644
index 0000000000000000000000000000000000000000..348b638843002926f57cdcf1d4fbc9bd88d2a10c
--- /dev/null
+++ b/20210107/bsort-1a.c
@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+ display (name, left, right);
+ usleep (200000);
+ return result;
+}
+
+void sort (char **name)
+{
+ for (int i = 1; name[i]; i++)
+ if (compare (name, i - 1, i) > 0)
+ {
+ char *temp = name[i - 1];
+ name[i - 1] = name[i];
+ name[i] = temp;
+ }
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Zacharias", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", NULL };
+ sort (name);
+ display (name, -1, -1);
+ return 0;
+}
diff --git a/20210107/bsort-2.c b/20210107/bsort-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..d277be0182a40ecd0c66eaeef94d7aebac6aa542
--- /dev/null
+++ b/20210107/bsort-2.c
@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+ display (name, left, right);
+ usleep (200000);
+ return result;
+}
+
+void sort (char **name)
+{
+ int sorted = 0;
+ while (name[sorted])
+ sorted++;
+ while (sorted > 0)
+ {
+ for (int i = 1; i < sorted; i++)
+ if (compare (name, i - 1, i) > 0)
+ {
+ char *temp = name[i - 1];
+ name[i - 1] = name[i];
+ name[i] = temp;
+ }
+ sorted--;
+ }
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ sort (name);
+ display (name, -1, -1);
+ return 0;
+}
diff --git a/20210107/bsort-3.c b/20210107/bsort-3.c
new file mode 100644
index 0000000000000000000000000000000000000000..67d0097b913171b4523f4f04b6b6ff494046dabd
--- /dev/null
+++ b/20210107/bsort-3.c
@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+ display (name, left, right);
+ usleep (200000);
+ return result;
+}
+
+void sort (char **name)
+{
+ int done = 0;
+ int sorted = 0;
+ while (name[sorted])
+ sorted++;
+ while (sorted > 0 && !done)
+ {
+ done = 1;
+ for (int i = 1; i < sorted; i++)
+ if (compare (name, i - 1, i) > 0)
+ {
+ done = 0;
+ char *temp = name[i - 1];
+ name[i - 1] = name[i];
+ name[i] = temp;
+ }
+ sorted--;
+ }
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ sort (name);
+ display (name, -1, -1);
+ return 0;
+}
diff --git a/20210107/bsort-4.c b/20210107/bsort-4.c
new file mode 100644
index 0000000000000000000000000000000000000000..241270a46f4ffa005d252207d769c3c4059ed7e2
--- /dev/null
+++ b/20210107/bsort-4.c
@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+ display (name, left, right);
+ usleep (200000);
+ return result;
+}
+
+void sort (char **name)
+{
+ int sorted = 0;
+ while (name[sorted])
+ sorted++;
+ while (sorted > 0)
+ {
+ int new_sorted = 0;
+ for (int i = 1; i < sorted; i++)
+ if (compare (name, i - 1, i) > 0)
+ {
+ new_sorted = i;
+ char *temp = name[i - 1];
+ name[i - 1] = name[i];
+ name[i] = temp;
+ }
+ sorted = new_sorted;
+ }
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ sort (name);
+ display (name, -1, -1);
+ return 0;
+}
diff --git a/20210107/hanoi-0.c b/20210107/hanoi-0.c
new file mode 100644
index 0000000000000000000000000000000000000000..83b5f081e33e699f2d5eaa1f858320530e1b2820
--- /dev/null
+++ b/20210107/hanoi-0.c
@@ -0,0 +1,26 @@
+#include <stdio.h>
+
+#define DISKS 4
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+int main (void)
+{
+ n[0] = 0;
+ n[1] = 0;
+ n[2] = 0;
+ display ();
+ return 0;
+}
diff --git a/20210107/hanoi-1.c b/20210107/hanoi-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..6d005f0b12afa6086afb65e1794fb5c977b474e2
--- /dev/null
+++ b/20210107/hanoi-1.c
@@ -0,0 +1,30 @@
+#include <stdio.h>
+
+#define DISKS 4
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+int main (void)
+{
+ n[0] = 4;
+ tower[0][0] = 4;
+ tower[0][1] = 3;
+ tower[0][2] = 2;
+ tower[0][3] = 1;
+ n[1] = 0;
+ n[2] = 0;
+ display ();
+ return 0;
+}
diff --git a/20210107/hanoi-2.c b/20210107/hanoi-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..c928c1130539da08d0882249bdffc877d72289b2
--- /dev/null
+++ b/20210107/hanoi-2.c
@@ -0,0 +1,28 @@
+#include <stdio.h>
+
+#define DISKS 4
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+int main (void)
+{
+ n[0] = DISKS;
+ for (int i = 0; i < DISKS; i++)
+ tower[0][i] = DISKS - i;
+ n[1] = 0;
+ n[2] = 0;
+ display ();
+ return 0;
+}
diff --git a/20210107/hanoi-3.c b/20210107/hanoi-3.c
new file mode 100644
index 0000000000000000000000000000000000000000..4b59c046962c1f79eca315882d93faf6b6c298c1
--- /dev/null
+++ b/20210107/hanoi-3.c
@@ -0,0 +1,44 @@
+#include <stdio.h>
+#include <error.h>
+
+#define DISKS 4
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+void move (int from, int to, int disks)
+{
+ if (disks == 1)
+ {
+ if (n[from] <= 0)
+ error (1, 0, "trying to move disk from empty tower");
+ if (n[to] > 0 && tower[to][n[to] - 1] < tower[from][n[from] - 1])
+ error (1, 0, "trying to move larger disk on smaller one");
+ tower[to][n[to]] = tower[from][n[from] - 1];
+ n[to]++;
+ n[from]--;
+ }
+}
+
+int main (void)
+{
+ n[0] = DISKS;
+ for (int i = 0; i < DISKS; i++)
+ tower[0][i] = DISKS - i;
+ n[1] = 0;
+ n[2] = 0;
+ move (2, 0, 1);
+ display ();
+ return 0;
+}
diff --git a/20210107/hanoi-4.c b/20210107/hanoi-4.c
new file mode 100644
index 0000000000000000000000000000000000000000..162a5ba7cccedf64bff8ae9a514aaf146088e3a4
--- /dev/null
+++ b/20210107/hanoi-4.c
@@ -0,0 +1,44 @@
+#include <stdio.h>
+#include <error.h>
+
+#define DISKS 4
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+void move (int from, int to, int disks)
+{
+ if (disks == 1)
+ {
+ if (n[from] <= 0)
+ error (1, 0, "trying to move disk from empty tower");
+ if (n[to] > 0 && tower[to][n[to] - 1] < tower[from][n[from] - 1])
+ error (1, 0, "trying to move larger disk on smaller one");
+ tower[to][n[to]] = tower[from][n[from] - 1];
+ n[to]++;
+ n[from]--;
+ }
+}
+
+int main (void)
+{
+ n[0] = DISKS;
+ for (int i = 0; i < DISKS; i++)
+ tower[0][i] = DISKS - i;
+ n[1] = 0;
+ n[2] = 0;
+ move (0, 2, 1);
+ display ();
+ return 0;
+}
diff --git a/20210107/hanoi-5.c b/20210107/hanoi-5.c
new file mode 100644
index 0000000000000000000000000000000000000000..e04ad85f63fe92e5c15d22646beb9e9107bf78d6
--- /dev/null
+++ b/20210107/hanoi-5.c
@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <error.h>
+
+#define DISKS 4
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+void move (int from, int to, int disks)
+{
+ if (disks == 1)
+ {
+ if (n[from] <= 0)
+ error (1, 0, "trying to move disk from empty tower");
+ if (n[to] > 0 && tower[to][n[to] - 1] < tower[from][n[from] - 1])
+ error (1, 0, "trying to move larger disk on smaller one");
+ tower[to][n[to]] = tower[from][n[from] - 1];
+ n[to]++;
+ n[from]--;
+ display ();
+ }
+}
+
+int main (void)
+{
+ n[0] = DISKS;
+ for (int i = 0; i < DISKS; i++)
+ tower[0][i] = DISKS - i;
+ n[1] = 0;
+ n[2] = 0;
+ display ();
+ move (0, 2, 1);
+ return 0;
+}
diff --git a/20210107/hanoi-6.c b/20210107/hanoi-6.c
new file mode 100644
index 0000000000000000000000000000000000000000..1267605f802246e857c32d29cc0a132609cb24ce
--- /dev/null
+++ b/20210107/hanoi-6.c
@@ -0,0 +1,52 @@
+#include <stdio.h>
+#include <error.h>
+
+#define DISKS 4
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+void move (int from, int to, int disks)
+{
+ if (disks == 1)
+ {
+ if (n[from] <= 0)
+ error (1, 0, "trying to move disk from empty tower");
+ if (n[to] > 0 && tower[to][n[to] - 1] < tower[from][n[from] - 1])
+ error (1, 0, "trying to move larger disk on smaller one");
+ tower[to][n[to]] = tower[from][n[from] - 1];
+ n[to]++;
+ n[from]--;
+ display ();
+ }
+ else
+ {
+ int help = 0 + 1 + 2 - from - to;
+ move (from, help, disks - 1);
+ move (from, to, 1);
+ move (help, to, disks - 1);
+ }
+}
+
+int main (void)
+{
+ n[0] = DISKS;
+ for (int i = 0; i < DISKS; i++)
+ tower[0][i] = DISKS - i;
+ n[1] = 0;
+ n[2] = 0;
+ display ();
+ move (0, 2, DISKS);
+ return 0;
+}
diff --git a/20210107/hanoi-7.c b/20210107/hanoi-7.c
new file mode 100644
index 0000000000000000000000000000000000000000..f71fcdc0c3f66047ee3ad870d019a06eb328050f
--- /dev/null
+++ b/20210107/hanoi-7.c
@@ -0,0 +1,52 @@
+#include <stdio.h>
+#include <error.h>
+
+#define DISKS 5
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+void move (int from, int to, int disks)
+{
+ if (disks == 1)
+ {
+ if (n[from] <= 0)
+ error (1, 0, "trying to move disk from empty tower");
+ if (n[to] > 0 && tower[to][n[to] - 1] < tower[from][n[from] - 1])
+ error (1, 0, "trying to move larger disk on smaller one");
+ tower[to][n[to]] = tower[from][n[from] - 1];
+ n[to]++;
+ n[from]--;
+ display ();
+ }
+ else
+ {
+ int help = 0 + 1 + 2 - from - to;
+ move (from, help, disks - 1);
+ move (from, to, 1);
+ move (help, to, disks - 1);
+ }
+}
+
+int main (void)
+{
+ n[0] = DISKS;
+ for (int i = 0; i < DISKS; i++)
+ tower[0][i] = DISKS - i;
+ n[1] = 0;
+ n[2] = 0;
+ display ();
+ move (0, 2, DISKS);
+ return 0;
+}
diff --git a/20210107/hanoi-8.c b/20210107/hanoi-8.c
new file mode 100644
index 0000000000000000000000000000000000000000..6d804063531d424a82924a89d85424c33994793b
--- /dev/null
+++ b/20210107/hanoi-8.c
@@ -0,0 +1,52 @@
+#include <stdio.h>
+#include <error.h>
+
+#define DISKS 64
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+void move (int from, int to, int disks)
+{
+ if (disks == 1)
+ {
+ if (n[from] <= 0)
+ error (1, 0, "trying to move disk from empty tower");
+ if (n[to] > 0 && tower[to][n[to] - 1] < tower[from][n[from] - 1])
+ error (1, 0, "trying to move larger disk on smaller one");
+ tower[to][n[to]] = tower[from][n[from] - 1];
+ n[to]++;
+ n[from]--;
+ display ();
+ }
+ else
+ {
+ int help = 0 + 1 + 2 - from - to;
+ move (from, help, disks - 1);
+ move (from, to, 1);
+ move (help, to, disks - 1);
+ }
+}
+
+int main (void)
+{
+ n[0] = DISKS;
+ for (int i = 0; i < DISKS; i++)
+ tower[0][i] = DISKS - i;
+ n[1] = 0;
+ n[2] = 0;
+ display ();
+ move (0, 2, DISKS);
+ return 0;
+}
diff --git a/20210107/hanoi-9.c b/20210107/hanoi-9.c
new file mode 100644
index 0000000000000000000000000000000000000000..7694b373b7011e96f6be0ad0f00ba54b67086158
--- /dev/null
+++ b/20210107/hanoi-9.c
@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <error.h>
+
+#define DISKS 64
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+void move (int from, int to, int disks)
+{
+ if (disks == 1)
+ {
+ if (n[from] <= 0)
+ error (1, 0, "trying to move disk from empty tower");
+ if (n[to] > 0 && tower[to][n[to] - 1] < tower[from][n[from] - 1])
+ error (1, 0, "trying to move larger disk on smaller one");
+ tower[to][n[to]] = tower[from][n[from] - 1];
+ n[to]++;
+ n[from]--;
+ static int counter = 1;
+ if (counter++ >= 100000000)
+ {
+ display ();
+ counter = 1;
+ }
+ }
+ else
+ {
+ int help = 0 + 1 + 2 - from - to;
+ move (from, help, disks - 1);
+ move (from, to, 1);
+ move (help, to, disks - 1);
+ }
+}
+
+int main (void)
+{
+ n[0] = DISKS;
+ for (int i = 0; i < DISKS; i++)
+ tower[0][i] = DISKS - i;
+ n[1] = 0;
+ n[2] = 0;
+ display ();
+ move (0, 2, DISKS);
+ display ();
+ return 0;
+}
diff --git a/20210107/hanoi-9a.c b/20210107/hanoi-9a.c
new file mode 100644
index 0000000000000000000000000000000000000000..55e8d74db6d7284d6db225a6f8f3e08ab4efdc06
--- /dev/null
+++ b/20210107/hanoi-9a.c
@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <error.h>
+
+#define DISKS 32
+
+int n[3], tower[3][DISKS];
+
+void display (void)
+{
+ printf ("\n");
+ for (int i = 0; i < 3; i++)
+ {
+ printf ("tower %d:", i);
+ for (int j = 0; j < n[i]; j++)
+ printf (" %d", tower[i][j]);
+ printf ("\n");
+ }
+}
+
+void move (int from, int to, int disks)
+{
+ if (disks == 1)
+ {
+ if (n[from] <= 0)
+ error (1, 0, "trying to move disk from empty tower");
+ if (n[to] > 0 && tower[to][n[to] - 1] < tower[from][n[from] - 1])
+ error (1, 0, "trying to move larger disk on smaller one");
+ tower[to][n[to]] = tower[from][n[from] - 1];
+ n[to]++;
+ n[from]--;
+ static int counter = 1;
+ if (counter++ >= 100000000)
+ {
+ display ();
+ counter = 1;
+ }
+ }
+ else
+ {
+ int help = 0 + 1 + 2 - from - to;
+ move (from, help, disks - 1);
+ move (from, to, 1);
+ move (help, to, disks - 1);
+ }
+}
+
+int main (void)
+{
+ n[0] = DISKS;
+ for (int i = 0; i < DISKS; i++)
+ tower[0][i] = DISKS - i;
+ n[1] = 0;
+ n[2] = 0;
+ display ();
+ move (0, 2, DISKS);
+ display ();
+ return 0;
+}
diff --git a/20210107/qsort-1.c b/20210107/qsort-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..c5431b853862e62812016f4fd3a031eeb0b5c9df
--- /dev/null
+++ b/20210107/qsort-1.c
@@ -0,0 +1,70 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, char *pivot, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (name[i] == pivot)
+ printf (" <==");
+ else if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, char *pivot, int left, int right)
+{
+ int result = strcmp (name[left], pivot);
+ comparisons++;
+ display (name, pivot, left, right);
+ usleep (200000);
+ return result;
+}
+
+void quicksort (char **name, int left, int right)
+{
+ int p = (left + right) / 2;
+ char *pivot = name[p];
+ int l = left;
+ int r = right;
+ while (l < r)
+ {
+ while (l < r && compare (name, pivot, l, r - 1) < 0)
+ l++;
+ while (l < r && compare (name, pivot, r - 1, l) > 0)
+ r--;
+ if (l < r)
+ {
+ char *temp = name[r - 1];
+ name[r - 1] = name[l];
+ name[l] = temp;
+ l++;
+ r--;
+ }
+ }
+}
+
+void sort (char **name)
+{
+ int r = 0;
+ while (name[r])
+ r++;
+ quicksort (name, 0, r);
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ sort (name);
+ display (name, NULL, -1, -1);
+ return 0;
+}
diff --git a/20210107/qsort-1a.c b/20210107/qsort-1a.c
new file mode 100644
index 0000000000000000000000000000000000000000..a3d4d0011834aa3d85907c2a0d0e90e3bf80799e
--- /dev/null
+++ b/20210107/qsort-1a.c
@@ -0,0 +1,70 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, char *pivot, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (name[i] == pivot)
+ printf (" <==");
+ else if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, char *pivot, int left, int right)
+{
+ int result = strcmp (name[left], pivot);
+ comparisons++;
+ display (name, pivot, left, right);
+ usleep (200000);
+ return result;
+}
+
+void quicksort (char **name, int left, int right)
+{
+ int p = (left + right) / 2 - 1;
+ char *pivot = name[p];
+ int l = left;
+ int r = right;
+ while (l < r)
+ {
+ while (l < r && compare (name, pivot, l, r - 1) < 0)
+ l++;
+ while (l < r && compare (name, pivot, r - 1, l) > 0)
+ r--;
+ if (l < r)
+ {
+ char *temp = name[r - 1];
+ name[r - 1] = name[l];
+ name[l] = temp;
+ l++;
+ r--;
+ }
+ }
+}
+
+void sort (char **name)
+{
+ int r = 0;
+ while (name[r])
+ r++;
+ quicksort (name, 0, r);
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ sort (name);
+ display (name, NULL, -1, -1);
+ return 0;
+}
diff --git a/20210107/qsort-2.c b/20210107/qsort-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..cfdc2ec11a92a4292c9443e01453cce818e9e73a
--- /dev/null
+++ b/20210107/qsort-2.c
@@ -0,0 +1,72 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, char *pivot, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (name[i] == pivot)
+ printf (" <==");
+ else if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, char *pivot, int left, int right)
+{
+ int result = strcmp (name[left], pivot);
+ comparisons++;
+ display (name, pivot, left, right);
+ usleep (200000);
+ return result;
+}
+
+void quicksort (char **name, int left, int right)
+{
+ int p = (left + right) / 2;
+ char *pivot = name[p];
+ int l = left;
+ int r = right;
+ while (l < r)
+ {
+ while (l < r && compare (name, pivot, l, r - 1) < 0)
+ l++;
+ while (l < r && compare (name, pivot, r - 1, l) > 0)
+ r--;
+ if (l < r)
+ {
+ char *temp = name[r - 1];
+ name[r - 1] = name[l];
+ name[l] = temp;
+ l++;
+ r--;
+ }
+ }
+ if (l < right)
+ quicksort (name, l, right);
+}
+
+void sort (char **name)
+{
+ int r = 0;
+ while (name[r])
+ r++;
+ quicksort (name, 0, r);
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ sort (name);
+ display (name, NULL, -1, -1);
+ return 0;
+}
diff --git a/20210107/qsort-3.c b/20210107/qsort-3.c
new file mode 100644
index 0000000000000000000000000000000000000000..e6b7d9909473af6d8c13d3745dc6b07e8ea75699
--- /dev/null
+++ b/20210107/qsort-3.c
@@ -0,0 +1,74 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, char *pivot, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (name[i] == pivot)
+ printf (" <==");
+ else if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, char *pivot, int left, int right)
+{
+ int result = strcmp (name[left], pivot);
+ comparisons++;
+ display (name, pivot, left, right);
+ usleep (200000);
+ return result;
+}
+
+void quicksort (char **name, int left, int right)
+{
+ int p = (left + right) / 2;
+ char *pivot = name[p];
+ int l = left;
+ int r = right;
+ while (l < r)
+ {
+ while (l < r && compare (name, pivot, l, r - 1) < 0)
+ l++;
+ while (l < r && compare (name, pivot, r - 1, l) > 0)
+ r--;
+ if (l < r)
+ {
+ char *temp = name[r - 1];
+ name[r - 1] = name[l];
+ name[l] = temp;
+ l++;
+ r--;
+ }
+ }
+ if (r > left)
+ quicksort (name, left, r);
+ if (l < right)
+ quicksort (name, l, right);
+}
+
+void sort (char **name)
+{
+ int r = 0;
+ while (name[r])
+ r++;
+ quicksort (name, 0, r);
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ sort (name);
+ display (name, NULL, -1, -1);
+ return 0;
+}
diff --git a/20210107/sort-0.c b/20210107/sort-0.c
new file mode 100644
index 0000000000000000000000000000000000000000..70e0e717cbfd42a27bf90f419c216fa18b0783c7
--- /dev/null
+++ b/20210107/sort-0.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+int find_first (char **name)
+{
+ return 2;
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ int first = find_first (name);
+ printf ("%s\n", name[first]);
+ return 0;
+}
diff --git a/20210107/sort-1.c b/20210107/sort-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..3f009d45657f84e462db48a67fa22821819216ad
--- /dev/null
+++ b/20210107/sort-1.c
@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <string.h>
+
+int find_first (char **name)
+{
+ int first = 0;
+ for (int i = 1; name[i]; i++)
+ if (strcmp (name[i], name[first]) < 0)
+ first = i;
+ return first;
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ int first = find_first (name);
+ printf ("%s\n", name[first]);
+ return 0;
+}
diff --git a/20210107/sort-2.c b/20210107/sort-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..638e6e2caa670ceace0a854d0827292dfcb59ca5
--- /dev/null
+++ b/20210107/sort-2.c
@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+ display (name, left, right);
+ usleep (200000);
+ return result;
+}
+
+int find_first (char **name)
+{
+ int first = 0;
+ for (int i = 1; name[i]; i++)
+ if (compare (name, i, first) < 0)
+ first = i;
+ return first;
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ int first = find_first (name);
+ display (name, first, -1);
+ return 0;
+}
diff --git a/20210107/sort-3.c b/20210107/sort-3.c
new file mode 100644
index 0000000000000000000000000000000000000000..430a6fc0e95fcb9bc225e3572566c8d187016130
--- /dev/null
+++ b/20210107/sort-3.c
@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+ display (name, left, right);
+ usleep (200000);
+ return result;
+}
+
+int find_first (char **name, int i0)
+{
+ int first = i0;
+ for (int i = i0 + 1; name[i]; i++)
+ if (compare (name, i, first) < 0)
+ first = i;
+ return first;
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ int first = find_first (name, 0);
+ display (name, first, -1);
+ return 0;
+}
diff --git a/20210107/sort-4.c b/20210107/sort-4.c
new file mode 100644
index 0000000000000000000000000000000000000000..19d4f416a2d30c5181ad289fe1d0dcba91ee81cf
--- /dev/null
+++ b/20210107/sort-4.c
@@ -0,0 +1,59 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+ display (name, left, right);
+ usleep (200000);
+ return result;
+}
+
+int find_first (char **name, int i0)
+{
+ int first = i0;
+ for (int i = i0 + 1; name[i]; i++)
+ if (compare (name, i, first) < 0)
+ first = i;
+ return first;
+}
+
+void sort (char **name)
+{
+ int sorted = 0;
+ while (name[sorted])
+ {
+ int first = find_first (name, sorted);
+ char *temp = name[sorted];
+ name[sorted] = name[first];
+ name[first] = temp;
+ sorted++;
+ }
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ sort (name);
+ display (name, -1, -1);
+ return 0;
+}
diff --git a/20210107/sort-5.c b/20210107/sort-5.c
new file mode 100644
index 0000000000000000000000000000000000000000..f0742bc8665d0b13edf4ad4ad3fe4790c1e6b929
--- /dev/null
+++ b/20210107/sort-5.c
@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+ display (name, left, right);
+ usleep (200);
+ return result;
+}
+
+int find_first (char **name, int i0)
+{
+ int first = i0;
+ for (int i = i0 + 1; name[i]; i++)
+ if (compare (name, i, first) < 0)
+ first = i;
+ return first;
+}
+
+void sort (char **name)
+{
+ int sorted = 0;
+ while (name[sorted])
+ {
+ int first = find_first (name, sorted);
+ char *temp = name[sorted];
+ name[sorted] = name[first];
+ name[first] = temp;
+ sorted++;
+ }
+}
+
+int main (void)
+{
+ char *name[] = {
+ #include "names.h"
+ NULL
+ };
+ sort (name);
+ display (name, -1, -1);
+ return 0;
+}
diff --git a/20210107/sort-6.c b/20210107/sort-6.c
new file mode 100644
index 0000000000000000000000000000000000000000..94a1a16abfacda7bb728f8d3317cd00b4cf8ccde
--- /dev/null
+++ b/20210107/sort-6.c
@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+// display (name, left, right);
+// usleep (200);
+ return result;
+}
+
+int find_first (char **name, int i0)
+{
+ int first = i0;
+ for (int i = i0 + 1; name[i]; i++)
+ if (compare (name, i, first) < 0)
+ first = i;
+ return first;
+}
+
+void sort (char **name)
+{
+ int sorted = 0;
+ while (name[sorted])
+ {
+ int first = find_first (name, sorted);
+ char *temp = name[sorted];
+ name[sorted] = name[first];
+ name[first] = temp;
+ sorted++;
+ }
+}
+
+int main (void)
+{
+ char *name[] = {
+ #include "names.h"
+ NULL
+ };
+ sort (name);
+ display (name, -1, -1);
+ return 0;
+}
diff --git a/20210107/sort-7.c b/20210107/sort-7.c
new file mode 100644
index 0000000000000000000000000000000000000000..46132dd247a061dda0e5ebade9c5b818a1a74fcb
--- /dev/null
+++ b/20210107/sort-7.c
@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int comparisons = 0;
+
+void display (char **name, int left, int right)
+{
+ printf ("\e[H\e[J");
+ for (int i = 0; name[i]; i++)
+ {
+ printf ("%s", name[i]);
+ if (i == left || i == right)
+ printf (" <--");
+ printf ("\n");
+ }
+ printf ("%d\n", comparisons);
+}
+
+int compare (char **name, int left, int right)
+{
+ int result = strcmp (name[left], name[right]);
+ comparisons++;
+ display (name, left, right);
+ usleep (200000);
+ return result;
+}
+
+void sort (char **name)
+{
+ int sorted = 0;
+ while (name[sorted])
+ {
+ int first = sorted;
+ for (int i = sorted + 1; name[i]; i++)
+ if (compare (name, i, first) < 0)
+ first = i;
+ char *temp = name[sorted];
+ name[sorted] = name[first];
+ name[first] = temp;
+ sorted++;
+ }
+}
+
+int main (void)
+{
+ char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
+ "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
+ "Thomas", "Ulrich", "Zacharias", NULL };
+ sort (name);
+ display (name, -1, -1);
+ return 0;
+}