Add 0049-group-anagrams.c

Author: seinlin

Diff for: c/0049-group-anagrams.c

@@ -0,0 +1,71 @@
+// Represent an elemet of the hash map.
+typedef struct {
+    char *key;
+    char *strs[100];
+    size_t size;
+    UT_hash_handle hh;
+} StrsHash;
+
+char *StrToKey(char *str) {
+    int size = strlen(str);
+    char c[26] = {0};
+    char *key = malloc(size + 1);
+    char *k = key;
+    size_t i, j;
+
+    for (i = 0; i < size; i++) {
+        c[str[i] - 'a']++;
+    }
+
+    for (i = 0; i < 26; i++) {
+        for (j = 0; j < c[i]; j++) {
+            *k++ = 'a' + i;
+        }
+    }
+    *k = '\0';
+    return key;
+}
+
+/**
+ * Return an array of arrays of size *returnSize.
+ * The sizes of the arrays are returned as *returnColumnSizes array.
+ * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
+ */
+char *** groupAnagrams(char ** strs, int strsSize, int* returnSize, int** returnColumnSizes){
+    StrsHash *map = NULL;
+    StrsHash *entry;
+    char *key = NULL;
+    char **resStrs = NULL;
+    char ***result = NULL;
+    int *colsSize = NULL;
+    size_t i;
+
+    // Create a hash map.
+    for (i = 0; i < strsSize; i++) {
+        entry = NULL;
+        key = StrToKey(strs[i]);
+        HASH_FIND_STR(map, key, entry);
+        if (!entry) {
+            entry = malloc(sizeof(StrsHash));
+            entry->key = key;
+            entry->size = 0;
+            HASH_ADD_KEYPTR(hh, map, key, strlen(key), entry);
+        } else {
+            free(key);
+        }
+        entry->strs[entry->size++] = strs[i];
+    }
+
+    // Prepare the answer from the hash map.
+    *returnSize = HASH_COUNT(map);
+    colsSize = (int*)malloc(*returnSize * sizeof(int));
+    result = (char***)malloc(*returnSize * sizeof(char**));
+    *returnColumnSizes = colsSize;
+
+    for (entry = map, i = 0; entry != NULL; entry = entry->hh.next, i++) {
+        colsSize[i] = entry->size;
+        result[i] = entry->strs;
+    }
+
+    return result;
+}