Find the total number of anagrams that a string contains of a substring

c/anagram.c

@@ -0,0 +1,62 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int compare(const void *lhs, const void *rhs) {
+  const char *left = lhs;
+  const char *right = rhs;
+  return *left > *right;
+}
+
+int main(int argc, char **argv) {
+  if(argc != 3) {
+    fprintf(stderr, "usage: %s <needle> <haystack>\n", argv[0]);
+    return 1;
+  }
+
+  char *needle = argv[1];
+  size_t needle_len = strlen(needle);
+  char *deeeln = malloc(needle_len);
+
+  if(!deeeln) {
+    fprintf(stderr, "malloc: %s\n", strerror(errno));
+    return 1;
+  }
+
+  strncpy(deeeln, needle, needle_len);
+  qsort(deeeln, needle_len, 1, compare);
+
+  char *haystack = argv[2];
+  size_t haystack_len = strlen(haystack);
+  char *aachksty = malloc(haystack_len);
+
+  if(!aachksty) {
+    fprintf(stderr, "malloc: %s\n", strerror(errno));
+    return 1;
+  }
+
+  size_t pos = 0;
+  char *idx = haystack;
+  unsigned int anagrams = 0;
+
+  for(; pos + needle_len <= haystack_len; pos += 1, idx += 1) {
+    strncpy(aachksty, idx, needle_len);
+    qsort(aachksty, needle_len, 1, compare);
+
+    if(strncmp(deeeln, aachksty, needle_len) == 0) {
+      anagrams += 1;
+    }
+  }
+
+  free(deeeln);
+  free(aachksty);
+  printf("%u anagram", anagrams);
+
+  if(anagrams != 1) {
+    printf("s");
+  }
+
+  printf("\n");
+  return 0;
+}