LeetCode 90. Subset II

Title Description

90. A subset of II

solution

We consider the method of backtracking , But and LeetCode 78. A subset of The difference is that we need to consider pruning , For example, for topic examples $nums=[1,2,2]$, The results generated without pruning are shown in the following figure

And the right result should be

So we have to prune , In the code , It needs to be sorted first , Put the same elements together , If you find that $nums[i]==nums[i-1]$, Then skip . See the following implementation for details

class Solution {
    
public:
    vector<vector<int>> res;

    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
    
        sort(nums.begin(), nums.end());
        vector<int> track;
        backtrace(nums, 0, track);
        return res;
    }

    void backtrace(vector<int>& nums, int start, vector<int> track)
    {
    
        res.push_back(track);

        for (int i = start; i < nums.size(); i++)
        {
    
            if (i > start && nums[i] == nums[i - 1]) continue;
            track.push_back(nums[i]);
            backtrace(nums, i + 1, track);
            track.pop_back();
        }
    }
};