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problems/0090.子集II.md

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+# 题目地址 
+https://leetcode-cn.com/problems/subsets-ii/
+# 第90题. 子集II
+
+
+# 思路 
+
+
+# C++代码
+
+```
+class Solution {
+private:
+    void backtracking(vector<int>& nums, vector<vector<int>>& result, vector<int>& vec, int startIndex,  vector<bool>& used) {
+        result.push_back(vec);
+        for (int i = startIndex; i < nums.size(); i++) {
+            if (i > 0 && nums[i] == nums[i - 1] && used[i-1] == false) { // 果然去重都是一个逻辑啊
+                continue;
+            }
+            vec.push_back(nums[i]);
+            used[i] = true;
+            backtracking(nums, result, vec, i + 1, used);
+            used[i] = false;
+            vec.pop_back();
+        }
+    }
+
+public:
+    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
+        vector<bool> used(nums.size(), false);
+        vector<vector<int>> result;
+        vector<int> vec;
+        sort(nums.begin(), nums.end());
+        backtracking(nums, result, vec, 0, used);
+        return result;
+    }
+};
+```