dfs就好了

先去重一下

class Solution {
public:
    vector<vector<int> > ret;
    int cnt[55], n;
    void dfs(vector<int> candidates, int target, int k, vector<int> v)
    {
        if (target < 0) return;
        if(k == n)
        {
            if(target == 0)
                ret.push_back(v);
            
 
return;
        }

        for(int i = 0; i <= cnt[candidates[k]]; i++)
        {
            if(i == 0) 
                dfs(candidates, target, k + 1, v);
            else
            {
                for(int j = 1; j <= i; j++)
                    v.push_back(candidates[k]);
                dfs(candidates, target 
 
- candidates[k] * i, k + 1, v);
                for(int j = 1; j <= i; j++)
                    v.erase(v.end() - 1);
            }        
        }
    }


    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {

        memset(cnt, 0, sizeof(cnt));
        vector
 
<int> v;
        int length = candidates.size();
        for(int i = 0; i < length; i++)
            cnt[candidates[i]]++;
        sort(candidates.begin(), candidates.end());
        candidates.erase(unique(candidates.begin(), candidates.end()), candidates.end());   
        n = candidates.size();
        dfs(candidates, target, 0, v);


        return ret;



    }
};