<p>Given a collection of candidate numbers (<code>candidates</code>) and a target number (<code>target</code>), find all unique combinations in <code>candidates</code>&nbsp;where the candidate numbers sum to <code>target</code>.</p>

<p>Each number in <code>candidates</code>&nbsp;may only be used <strong>once</strong> in the combination.</p>

<p><strong>Note:</strong>&nbsp;The solution set must not contain duplicate combinations.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> candidates = [10,1,2,7,6,1,5], target = 8
<strong>Output:</strong> 
[
[1,1,6],
[1,2,5],
[1,7],
[2,6]
]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> candidates = [2,5,2,1,2], target = 5
<strong>Output:</strong> 
[
[1,2,2],
[5]
]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;=&nbsp;candidates.length &lt;= 100</code></li>
	<li><code>1 &lt;=&nbsp;candidates[i] &lt;= 50</code></li>
	<li><code>1 &lt;= target &lt;= 30</code></li>
</ul>

class Solution {
public:
    void search(int cur,vector<int> vec,vector<vector<int>>& result,int tar,vector<int> count)
    {
        if(cur>tar) cur = tar;
        if(count[cur]==0){
            for(;count[cur]==0&&cur>0;cur--);
        }
        if(cur==0) return;

        search(cur-1,vec,result,tar,count);

        for(int i = 1;i<=count[cur];i++){
            if(cur*i>tar) break;
            vec.push_back(cur);
            if(tar==i*cur){
                result.push_back(vec);
            }
            else{
                search(cur-1,vec,result,tar-i*cur,count);
            }

        }


    }
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        vector<int> count(31,0);
        for(int c:candidates){
            if(c<=target){
                count[c]++;
            }
        }
        vector<vector<int>> result;
        vector<int> vec;
        search(target,vec,result,target,count);
        return result;
    }
    
};
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