1 files changed, 46 insertions, 0 deletions
diff --git a/Computer_Science/leetcode/17-letter_combinations_of_a_phone_number.c b/Computer_Science/leetcode/17-letter_combinations_of_a_phone_number.c
new file mode 100644
index 0000000..eeabd21
--- /dev/null
+++ b/Computer_Science/leetcode/17-letter_combinations_of_a_phone_number.c
@@ -0,0 +1,46 @@
+/**
+ * Return an array of size *returnSize.
+ * Note: The returned array must be malloced, assume caller calls free().
+ */
+void helper(char **result, char *map[10], char *digits, char *tmp, int index, int *returnSize)
+{
+	char *p = map[*digits - '0'];
+	for(; *p; ++p) {
+		tmp[index] = *p;
+		helper(result, map, digits + 1, tmp, index + 1, returnSize);
+	}
+	if(*digits == '\0') {
+		*(result + *returnSize) = malloc(sizeof(char) * index + 1);
+		for(int i = 0; i < index; i++) {
+			*(*(result + *returnSize) + i) = tmp[i];
+		}
+		*(*(result + *returnSize) + index) = '\0';
+		++*returnSize;
+	}
+}
+char** letterCombinations(char* digits, int* returnSize) {
+	int len = strlen(digits);
+	int index = 0;
+	char tmp[len + 1];
+	char **result = malloc(sizeof(int *) * 100);
+	char *map[10] = {
+		" ", " ", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"
+	};
+
+	*returnSize = 0;
+
+	if(len < 1)
+		return result;
+
+	while(*digits) {
+		if(*digits >= '2' && *digits <= '9') {
+			helper(result, map, digits, tmp, index, returnSize);
+		} else {
+			*returnSize = 0;
+			break;
+		}
+		++digits;
+	}
+
+	return result;
+}