添加 0078.子集.md C语言版本

problems/0078.子集.md

@@ -263,6 +263,63 @@ var subsets = function(nums) {
 };
 ```
 
+C:
+```c
+int* path;
+int pathTop;
+int** ans;
+int ansTop;
+//记录二维数组中每个一维数组的长度
+int* length;
+//将当前path数组复制到ans中
+void copy() {
+    int* tempPath = (int*)malloc(sizeof(int) * pathTop);
+    int i;
+    for(i = 0; i < pathTop; i++) {
+        tempPath[i] = path[i];
+    }
+    ans = (int**)realloc(ans, sizeof(int*) * (ansTop+1));
+    length[ansTop] = pathTop;
+    ans[ansTop++] = tempPath;
+}
+
+void backTracking(int* nums, int numsSize, int startIndex) {
+    //收集子集，要放在终止添加的上面，否则会漏掉自己
+    copy();
+    //若startIndex大于数组大小，返回
+    if(startIndex >= numsSize) {
+        return;
+    }
+    int j;
+    for(j = startIndex; j < numsSize; j++) {
+        //将当前下标数字放入path中
+        path[pathTop++] = nums[j];
+        backTracking(nums, numsSize, j+1);
+        //回溯
+        pathTop--;
+    }
+}
+
+int** subsets(int* nums, int numsSize, int* returnSize, int** returnColumnSizes){
+    //初始化辅助变量
+    path = (int*)malloc(sizeof(int) * numsSize);
+    ans = (int**)malloc(0);
+    length = (int*)malloc(sizeof(int) * 1500);
+    ansTop = pathTop = 0;
+    //进入回溯
+    backTracking(nums, numsSize, 0);
+    //设置二维数组中元素个数
+    *returnSize = ansTop;
+    //设置二维数组中每个一维数组的长度
+    *returnColumnSizes = (int*)malloc(sizeof(int) * ansTop);
+    int i;
+    for(i = 0; i < ansTop; i++) {
+        (*returnColumnSizes)[i] = length[i];
+    }
+    return ans;
+}
+```
+
 
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 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)