<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>> ans;
    int n;
    void helper(int ele,vector<int> &v,int target,vector<int> &val){
        if(target==0){
            ans.push_back(val);
            return;
        }
        if(ele>target){
            return;
        }
        if(v[ele]>0){
            v[ele]--;
            val.push_back(ele);
            helper(ele,v,target-ele,val);
            val.pop_back();
            v[ele]++;
        }
        helper(ele+1,v,target,val);
    }
    vector<vector<int>> combinationSum2(vector<int>& nums, int target) {
        n=nums.size();
        vector<int> v(51,0);
        for(int i=0;i<n;i++){
            v[nums[i]]++;
        }
        vector<int> val;
        helper(0,v,target,val);
        return ans;
    }
};
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