<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;
    void solve(int index, int left,vector<pair<int,int>> &v, vector<int> &temp)
    {
        if(left == 0)
        {
            ans.push_back(temp);
            return ;
        }
        else if(left < 0) return ;
        if(index >= v.size()) return ;

        int freq = v[index].second, ele = v[index].first;
        solve(index+1,left,v,temp);
        int i;
        for(i = 1 ; i <= freq ; i++)
        {
            if(left - i*ele >= 0)
            {
                temp.push_back(ele);
                solve(index+1,left-i*ele,v,temp);
            }
            else break;
        }
        i--;
        while(i--) temp.pop_back();
    }
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        map<int,int> mp;
        for(int i = 0 ; i < candidates.size() ; i++)
        {
            mp[candidates[i]]++;
        }
        vector<pair<int,int>> v;
        for(auto &it : mp) v.push_back(it);

        vector<int> temp;
        solve(0,target,v,temp);
        return ans;
    }
};
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