<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 combinationSumHelper(int& i,vector<int>& arr, int& target, vector<int>& curr, vector<vector<int>>& res){
        if(i == arr.size()){
            if(!target)
                res.push_back(curr);
            return;
        }
        int orgTarget = target;
        int j = i;
        int k = i;
        while(j<arr.size()-1 && arr[j] == arr[j+1]){
            j++;
        }
        i=j+1;
        combinationSumHelper(i, arr, target, curr, res);
        while(j>=k && target >= arr[k]){
            target -= arr[k];
            curr.push_back(arr[k]);
            combinationSumHelper(i, arr, target, curr, res);
            j--;
        }
        i=k;
        target = orgTarget;
        while(!curr.empty() && curr.back() == arr[i]){
            curr.pop_back();
        }
    }

    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        sort(candidates.begin(), candidates.end());
        vector<vector<int>> res;
        vector<int> curr;
        int i=0;
        combinationSumHelper(i, candidates, target, curr, res);
        return res;
    }
};
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