diff --git a/20220428/hash-map-1.c b/20220428/hash-map-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..ac4e69a997c9bb334c51726867d81972363b5ac6
--- /dev/null
+++ b/20220428/hash-map-1.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+#include <string.h>
+
+int get_number (const char *name) /* geschummelt, aber trotzdem schlechter als die */
+{ /* richtige Lösung: O(n) statt O(1) */
+ if (!strcmp (name, "eins"))
+ return 1;
+ else if (!strcmp (name, "zwei"))
+ return 2;
+ else if (!strcmp (name, "drei"))
+ return 3;
+ else
+ return 0;
+}
+
+int main (void)
+{
+ int eins = get_number ("eins");
+ int zwei = get_number ("zwei");
+ int drei = get_number ("drei");
+ printf ("%d %d %d\n", eins, zwei, drei);
+ return 0;
+}
diff --git a/20220428/hash-map-2.c b/20220428/hash-map-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..ad282b0476fc916d70459f9884f1e99e41edbf0a
--- /dev/null
+++ b/20220428/hash-map-2.c
@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <string.h>
+
+int get_number (const char *name) /* geschummelt, aber trotzdem schlechter als die */
+{ /* richtige Lösung: O(n) statt O(1) */
+ static const char *n[] = { "null", "eins", "zwei", "drei", "vier", NULL };
+ for (int i = 0; n[i]; i++)
+ if (!strcmp (name, n[i]))
+ return i;
+ return -1;
+}
+
+int main (void)
+{
+ int eins = get_number ("eins");
+ int zwei = get_number ("zwei");
+ int drei = get_number ("drei");
+ printf ("%d %d %d\n", eins, zwei, drei);
+ return 0;
+}
diff --git a/20220428/hash-map-3.c b/20220428/hash-map-3.c
new file mode 100644
index 0000000000000000000000000000000000000000..bf0c603a0170e45aa422e5c2b1594da94de4b248
--- /dev/null
+++ b/20220428/hash-map-3.c
@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <string.h>
+
+int get_number (const char *name) /* nicht mehr geschummelt, O(1), aber: */
+{ /* - Speicher-ineffizient */
+ static const int n[26] = /* - unvollständig: "sechs", "sieben" */
+ { /* - unzuverlässig: "egon" = "eins" */
+ 8, /* a */
+ -1, /* b */
+ -1, /* c */
+ 3, /* d */
+ 1, /* e */
+ 5, /* f */
+ -1, /* g */
+ -1, /* h */
+ -1, /* i */
+ -1, /* j */
+ -1, /* k */
+ -1, /* l */
+ -1, /* m */
+ 0, /* n */
+ -1, /* o */
+ -1, /* p */
+ -1, /* q */
+ -1, /* r */
+ 6, /* s */
+ -1, /* t */
+ -1, /* u */
+ 4, /* v */
+ -1, /* w */
+ -1, /* x */
+ -1, /* y */
+ 2 /* z */
+ };
+ int value = -1;
+ if (name && name[0] >= 'a' && name[0] <= 'z')
+ value = n[name[0] - 'a'];
+ return value;
+}
+
+int main (void)
+{
+ int eins = get_number ("egon");
+ int zwei = get_number ("zwei");
+ int drei = get_number ("drei");
+ int vier = get_number ("vier");
+ printf ("%d %d %d %d\n", eins, zwei, drei, vier);
+ return 0;
+}
diff --git a/20220428/hash-map-4.c b/20220428/hash-map-4.c
new file mode 100644
index 0000000000000000000000000000000000000000..f2f4ac79bc8b65ecb78314afd69dcd7a0be1dce6
--- /dev/null
+++ b/20220428/hash-map-4.c
@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <string.h>
+
+int get_number (const char *name) /* nicht mehr geschummelt, O(1), aber: */
+{ /* - Speicher-ineffizient */
+ static const int n[26] = /* - unvollständig: "sechs", "sieben" */
+ { /* :) zuverlässig: "egon" != "eins" */
+ 8, /* a */
+ -1, /* b */
+ -1, /* c */
+ 3, /* d */
+ 1, /* e */
+ 5, /* f */
+ -1, /* g */
+ -1, /* h */
+ -1, /* i */
+ -1, /* j */
+ -1, /* k */
+ -1, /* l */
+ -1, /* m */
+ 0, /* n */
+ -1, /* o */
+ -1, /* p */
+ -1, /* q */
+ -1, /* r */
+ 6, /* s */
+ -1, /* t */
+ -1, /* u */
+ 4, /* v */
+ -1, /* w */
+ -1, /* x */
+ -1, /* y */
+ 2 /* z */
+ };
+ static const char *check[26] =
+ {
+ "acht",
+ NULL, /* b */
+ NULL, /* c */
+ "drei",
+ "eins",
+ "fünf",
+ NULL, /* g */
+ NULL, /* h */
+ NULL, /* i */
+ NULL, /* j */
+ NULL, /* k */
+ NULL, /* l */
+ NULL, /* m */
+ "null",
+ NULL, /* o */
+ NULL, /* p */
+ NULL, /* q */
+ NULL, /* r */
+ "sechs",
+ NULL, /* t */
+ NULL, /* u */
+ "vier",
+ NULL, /* w */
+ NULL, /* x */
+ NULL, /* y */
+ "zwei"
+ };
+ int value = -1;
+ if (name && name[0] >= 'a' && name[0] <= 'z')
+ {
+ int i = name[0] - 'a';
+ if (!strcmp (name, check[i]))
+ value = n[i];
+ }
+ return value;
+}
+
+int main (void)
+{
+ int eins = get_number ("egon");
+ int zwei = get_number ("zwei");
+ int drei = get_number ("drei");
+ int vier = get_number ("vier");
+ printf ("%d %d %d %d\n", eins, zwei, drei, vier);
+ return 0;
+}
diff --git a/20220428/hash-map-5.c b/20220428/hash-map-5.c
new file mode 100644
index 0000000000000000000000000000000000000000..cc67f01626db2f109677f56a16c721be3ecb1653
--- /dev/null
+++ b/20220428/hash-map-5.c
@@ -0,0 +1,90 @@
+#include <stdio.h>
+#include <string.h>
+
+int get_number (const char *name) /* nicht mehr geschummelt, O(1), aber: */
+{ /* - Speicher-ineffizient */
+ static const int n[26] = /* :] vollständig: "sechs" != "sieben", aber unschön */
+ { /* :) zuverlässig: "egon" != "eins" */
+ 8, /* a */
+ -1, /* b */
+ -1, /* c */
+ 3, /* d */
+ 1, /* e */
+ 5, /* f */
+ -1, /* g */
+ -1, /* h */
+ -1, /* i */
+ -1, /* j */
+ -1, /* k */
+ -1, /* l */
+ -1, /* m */
+ 0, /* n */
+ -1, /* o */
+ -1, /* p */
+ -1, /* q */
+ -1, /* r */
+ 6, /* s */
+ -1, /* t */
+ -1, /* u */
+ 4, /* v */
+ -1, /* w */
+ -1, /* x */
+ -1, /* y */
+ 2 /* z */
+ };
+ static const char *check[26] =
+ {
+ "acht",
+ NULL, /* b */
+ NULL, /* c */
+ "drei",
+ "eins",
+ "fünf",
+ NULL, /* g */
+ NULL, /* h */
+ NULL, /* i */
+ NULL, /* j */
+ NULL, /* k */
+ NULL, /* l */
+ NULL, /* m */
+ "null",
+ NULL, /* o */
+ NULL, /* p */
+ NULL, /* q */
+ NULL, /* r */
+ "sechs",
+ NULL, /* t */
+ NULL, /* u */
+ "vier",
+ NULL, /* w */
+ NULL, /* x */
+ NULL, /* y */
+ "zwei"
+ };
+ int value = -1;
+ if (name && name[0] >= 'a' && name[0] <= 'z')
+ {
+ if (name[0] == 's' && !strcmp (name, "sieben"))
+ value = 7;
+ else
+ {
+ int i = name[0] - 'a';
+ if (!strcmp (name, check[i]))
+ value = n[i];
+ }
+ }
+ return value;
+}
+
+int main (void)
+{
+ int eins = get_number ("eins");
+ int zwei = get_number ("zwei");
+ int drei = get_number ("drei");
+ int vier = get_number ("vier");
+ int fuenf = get_number ("fünf");
+ int sechs = get_number ("sechs");
+ int sieben = get_number ("sieben");
+ printf ("%d %d %d %d %d %d %d\n", eins, zwei, drei, vier, fuenf, sechs, sieben);
+ return 0;
+}
diff --git a/20220428/hash-map-6.c b/20220428/hash-map-6.c
new file mode 100644
index 0000000000000000000000000000000000000000..64a725c75ad13dad5c516657dbe5e1c77a1d0099
--- /dev/null
+++ b/20220428/hash-map-6.c
@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include <string.h>
+
+int n[65536]; /* zunächst: alle 0 */
+const char *check[65536]; /* zunächst: alle NULL */
+
+void put_number (const char *name, int value)
+{
+ /* Nimm die ersten 2 Zeichen des Strings,
+ * berechne daraus einen Array-Index von 0 bis 65535.
+ * Dort hinterlege die Zahl "value" im Array.
+ */
+}
+
+int get_number (const char *name) /* nicht mehr geschummelt, O(1), aber: */
+{ /* - Speicher-ineffizient */
+ int value = -1;
+ /* Nimm die ersten 2 Zeichen des Strings,
+ * berechne daraus einen Array-Index von 0 bis 65535.
+ * Dort entnimm die Zahl "value".
+ */
+ return value;
+}
+
+int main (void)
+{
+ put_number ("eins", 1);
+ put_number ("zwei", 2);
+ put_number ("drei", 3);
+ put_number ("vier", 4);
+ put_number ("fünf", 5);
+ put_number ("sechs", 6);
+ put_number ("sieben", 7);
+ put_number ("acht", 8);
+ put_number ("neun", 9);
+ put_number ("zehn", 10);
+ int eins = get_number ("eins");
+ int zwei = get_number ("zwei");
+ int drei = get_number ("drei");
+ int vier = get_number ("vier");
+ int fuenf = get_number ("fünf");
+ int sechs = get_number ("sechs");
+ int sieben = get_number ("sieben");
+ printf ("%d %d %d %d %d %d %d\n", eins, zwei, drei, vier, fuenf, sechs, sieben);
+ return 0;
+}