<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:
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        sort(candidates.begin(),candidates.end());

        int sum = 0;
        int index = 0;
        vector<int>temp = {};
        vector<vector<int>>answer;

        backtrack(temp,index,sum,candidates,target,answer);

        return answer;
    }

    void backtrack(vector<int>temp,int index,int sum,vector<int>candidates,int target,vector<vector<int>>&answer){
        
        if(sum == target){
            answer.push_back(temp);
            return;
        }

        for(int i = index;i < candidates.size();i++){

            if(i == index || candidates[i] != candidates[i-1]){
                sum += candidates[i];
                
                if(sum > target) break;

                temp.push_back(candidates[i]);

                backtrack(temp,i+1,sum,candidates,target,answer);

                sum -= candidates[i];
                temp.pop_back();
            }
            
        }

        return;
    }
};
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