添加 0040.组合总和II.md C语言版本

problems/0040.组合总和II.md

@@ -392,7 +392,66 @@ var combinationSum2 = function(candidates, target) {
     }
 };
 ```
+C:
+```c
+int* path;
+int pathTop;
+int** ans;
+int ansTop;
+//记录ans中每一个一维数组的大小
+int* length;
+int cmp(const void* a1, const void* a2) {
+    return *((int*)a1) - *((int*)a2);
+}
 
+void backTracking(int* candidates, int candidatesSize,  int target, int sum, int startIndex) {
+    if(sum >= target) {
+        //若sum等于target，复制当前path进入
+        if(sum == target) {
+            int* tempPath = (int*)malloc(sizeof(int) * pathTop);
+            int j;
+            for(j = 0; j < pathTop; j++) {
+                tempPath[j] = path[j];
+            }
+            length[ansTop] = pathTop;
+            ans[ansTop++] = tempPath;
+        }
+        return ;
+    }
+
+    int i;
+    for(i = startIndex; i < candidatesSize; i++) {
+        //对同一层树中使用过的元素跳过
+        if(i > startIndex && candidates[i] == candidates[i-1])
+            continue;
+        path[pathTop++] = candidates[i];
+        sum += candidates[i];
+        backTracking(candidates, candidatesSize, target, sum, i + 1);
+        //回溯
+        sum -= candidates[i];
+        pathTop--;
+    }
+}
+
+int** combinationSum2(int* candidates, int candidatesSize, int target, int* returnSize, int** returnColumnSizes){
+    path = (int*)malloc(sizeof(int) * 50);
+    ans = (int**)malloc(sizeof(int*) * 100);
+    length = (int*)malloc(sizeof(int) * 100);
+    pathTop = ansTop = 0;
+    //快速排序candidates，让相同元素挨到一起
+    qsort(candidates, candidatesSize, sizeof(int), cmp);
+
+    backTracking(candidates, candidatesSize, target, 0, 0);
+
+    *returnSize = ansTop;
+    *returnColumnSizes = (int*)malloc(sizeof(int) * ansTop);
+    int i;
+    for(i = 0; i < ansTop; i++) {
+        (*returnColumnSizes)[i] = length[i];
+    }
+    return ans;
+}
+```
 
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)