<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 helper(vector<int> candidates,int target,vector<vector<int>>& combs,int level,vector<int> tmp){
        if(target == 0){
            combs.push_back(tmp);
            return;
        }
        else if(level == candidates.size()){
            return;
        }
        else if(candidates[level] > target){
            return;
        }

        if(candidates[level] <= target){
            tmp.push_back(candidates[level]);
            helper(candidates,target-candidates[level],combs,level+1,tmp);
            tmp.pop_back();
        }
        int num = candidates[level];
        while(level < candidates.size() && candidates[level]==num){
            level++;
        }
        helper(candidates,target,combs,level,tmp);
    }
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        vector<vector<int>> combs;
        sort(candidates.begin(),candidates.end());
        vector<int> tmp = {};
        helper(candidates,target,combs,0,tmp);
        return combs;
    }
};
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