[0739 temperature] add C version

add C version for 0739: temperature

Signed-off-by: liao junwu <andyliaowu5@163.com>

problems/0739.每日温度.md

@@ -215,6 +215,38 @@ public:
 
 ## 其他语言版本
 
+### C：
+
+```C
+/**
+ * Note: The returned array must be malloced, assume caller calls free().
+ */
+int* dailyTemperatures(int* temperatures, int temperaturesSize, int* returnSize) {
+    int len = temperaturesSize;
+    *returnSize = len;
+
+    int *result = (int *)malloc(sizeof(int) * len);
+    memset(result, 0x00, sizeof(int) * len);
+
+    int stack[len];
+    memset(stack, 0x00, sizeof(stack));
+    int top = 0;
+
+    for (int i = 1; i < len; i++) {
+        if (temperatures[i] <= temperatures[stack[top]]) { /* push */
+            stack[++top] = i;
+        } else {
+            while (top >= 0 && temperatures[i] > temperatures[stack[top]]) { /* stack not empty */
+                result[stack[top]] = i - stack[top];
+                top--; /* pop */
+            }
+            stack[++top] = i; /* push */
+        }
+    }
+    return result;
+}
+```
+
 ### Java：
 
 ```java