<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 combinationsum2(vector<pair<int,int>>& pcandidates, int target, int i, vector<int>ds,vector<vector<int>>& subset){
//base case
if(target==0){subset.push_back(ds);return ;}
if(i==pcandidates.size()){return ;}

//nottake
combinationsum2(pcandidates,target,i+1,ds,subset);
//take
for(int k=1 ; k<=pcandidates[i].second;k++){
// for(int j = 0 ; j<k;j++){
    ds.push_back(pcandidates[i].first);
    // }
    if(target<pcandidates[i].first*k)break;
combinationsum2(pcandidates, target-pcandidates[i].first*k, i+1 , ds, subset);
// for(int j = 0 ; j<k;j++){ds.pop_back();}
}
return;
}

    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {

vector<vector<int>> subset;
vector<int> ds;
unordered_map<int,int> mf;
sort(candidates.begin(),candidates.end());
for(int i =0;i<candidates.size();i++) mf[candidates[i]]++;

vector<pair<int,int>> pcandidates;
for(auto i :mf) pcandidates.push_back({i.first,i.second});

     combinationsum2(pcandidates, target,0,ds,subset)   ;
     return subset;
    }
};
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