<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:
    // map<pair<int,int>, vector<vector<int> > > dp;

    // vector<vector<int> > solve(int index, int target, vector<int>& candidates)
    // {
    //     if(target==0) vector<vector<int> > ();
    //     if(target<0) return vector<vector<int> > ();
    //     if(index==candidates.size()) return vector<vector<int> > ();
    //     if(dp.count(make_pair(index,target))>0) return dp[make_pair(index,target)];

    //     vector<vector<int> > take, notTake;

    //     //take

    //     take = solve(index+1,target-candidates[index],candidates);

    //     for(auto &x:take)
    //     {
    //         x.push_back(candidates[index]);
    //     }

    //     //not take

    //     notTake = solve(index+1, target, candidates);

    //     for(auto x:notTake)
    //     {
    //         take.push_back(x);
    //     }

    //     return dp[make_pair(index,target)]=take;
    // }

    set<vector<int> > ans;
    vector<int> path;

    void solve(int index, int target, vector<int>& candidates, bool taken)
    {
        if(target==0) 
        {
            ans.insert(path);
            return;
        }
        if(target<0) return;
        if(index==candidates.size()) return;

        if(taken || (index>=1 && candidates[index]!=candidates[index-1]) || index==0)
        {

            path.push_back(candidates[index]);
            solve(index+1, target-candidates[index], candidates, 1);
            path.pop_back();
        }

        solve(index+1, target, candidates, 0);

        return;
    }

    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) 
    {
        ans.clear();
        path.clear();
        path.reserve(100);


        sort(candidates.begin(), candidates.end());

        vector<vector<int> > result;
        result.reserve(10000);

        solve(0,target,candidates, 0);

        for(auto &x:ans) result.push_back(x);

        return result;
    }
};
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