add random stuffs

levenshtein.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <stdlib.h>
+#include <string.h>
+
+#ifndef min
+#define min(a, b) ((a) < (b) ? (a) : (b))
+#endif
+
+#ifndef min3
+#define min3(a, b, c) (min(min(a, b), c))
+#endif
+
+static inline int levenshtein(const char* s1, const char* s2) {
+    int len1 = strlen(s1);
+    int len2 = strlen(s2);
+
+    int* row = malloc((len2 + 1) * sizeof(int));
+    if (!row) return -1;
+
+    for (int j = 0; j <= len2; j++)
+        row[j] = j;
+
+    for (int i = 1; i <= len1; i++) {
+        int prev_diag = row[0];
+        row[0] = i;
+        for (int j = 1; j <= len2; j++) {
+            int temp = row[j];
+            row[j] = min3(
+                row[j] + 1,                      // deletion
+                row[j-1] + 1,                    // insertion
+                prev_diag + (s1[i-1] != s2[j-1]) // substitution
+            );
+            prev_diag = temp;
+        }
+    }
+
+    int result = row[len2];
+    free(row);
+    return result;
+}