Beispiel-Programme 7.1.2021

20210107/bsort-1.c

+#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;
+}

20210107/bsort-1a.c

+#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;
+}

20210107/bsort-2.c

+#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;
+}

20210107/bsort-3.c

+#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;
+}

20210107/bsort-4.c

+#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;
+}

20210107/hanoi-0.c

+#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;
+}

20210107/hanoi-1.c

+#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;
+}

20210107/hanoi-2.c

+#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;
+}

20210107/hanoi-3.c

+#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;
+}

20210107/hanoi-4.c

+#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;
+}

20210107/hanoi-5.c

+#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;
+}

20210107/hanoi-6.c

+#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;
+}

20210107/hanoi-7.c

+#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;
+}

20210107/hanoi-8.c

+#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;
+}

20210107/hanoi-9.c

+#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;
+}

20210107/hanoi-9a.c

+#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;
+}

20210107/qsort-1.c

+#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;
+}

20210107/qsort-1a.c

+#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;
+}

20210107/qsort-2.c

+#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;
+}

20210107/qsort-3.c

+#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;
+}