Update 78. Subsets.md

solutions/78. Subsets.md

@@ -23,6 +23,33 @@
 
 # C++
 ## 思路一
+### 好理解版
+``` C++
+class Solution {
+private:
+    void DFS(vector<vector<int>>&res, vector<int>&subset, const vector<int>& nums, int level){
+        if(level == nums.size()) {  // 到达叶节点
+            res.push_back(subset);
+            return;
+        }
+        // 向左子树下降
+        subset.push_back(nums[level]);
+        DFS(res, subset, nums, level + 1);
+        subset.pop_back();
+        // 向右子树下降
+        DFS(res, subset, nums, level + 1);
+    }
+public:
+    vector<vector<int>> subsets(vector<int>& nums) {
+        vector<vector<int>>res;
+        vector<int>subset;
+        sort(nums.begin(), nums.end());
+        DFS(res, subset, nums, 0);
+        return res;
+    }
+};
+```
+### 简洁版
 ``` C++
 class Solution {
 private: