Merge pull request neetcode-gh#2220 from seinlin/438

Add 0438-find-all-anagrams-in-a-string.c

c/0438-find-all-anagrams-in-a-string.c

@@ -0,0 +1,47 @@
+#define TO_INDEX(c) c - 'a'
+
+bool isEquals(int* a, int* b, int n) {
+ for (int i = 0; i < n; i++) {
+ if (a[i] != b[i]) {
+ return false;
+ }
+ }
+ return true;
+}
+
+/**
+ * Note: The returned array must be malloced, assume caller calls free().
+ */
+int* findAnagrams(char * s, char * p, int* returnSize) {
+ int sSize = strlen(s);
+ int pSize = strlen(p);
+ int pFreq[26] = {0};
+ int sFreq[26] = {0};
+ int i, count;
+ int* ans;
+
+ if (sSize < pSize) {
+ *returnSize = 0;
+ return ans;
+ }
+
+ for (i = 0; i < pSize; i++) {
+ pFreq[TO_INDEX(p[i])]++;
+ sFreq[TO_INDEX(s[i])]++;
+ }
+
+ count = 0;
+ ans = (int*)calloc(sSize - pSize + 1, sizeof(int));
+ for (i = 0; i <= sSize - pSize; i++) {
+ if (i > 0) {
+ sFreq[TO_INDEX(s[i - 1])]--;
+ sFreq[TO_INDEX(s[i + pSize - 1])]++;
+ }
+ if (isEquals(sFreq, pFreq, 26)) {
+ ans[count++] = i;
+ }
+ }
+ *returnSize = count;
+
+ return ans;
+}