<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 allCombToSum(vector<int> candidates, vector<vector<int>>& ans, vector<int>& comb, int idx, int target)
    {
        
        // BASE CASE 1
        if (target == 0)
        {
            ans.push_back(comb);
            return;
        }
        
        // BASE CASE 2
        if (idx == candidates.size() || candidates[idx] > target) return;

        // ELSE pick ...
        comb.push_back(candidates[idx]);
        allCombToSum(candidates, ans, comb, idx+1, target - candidates[idx]);
        comb.pop_back();
        
        // ... and non-pick by recursing on the next available candidate 
        // which is not the same as the current candidate.
        idx++;
        while (idx < candidates.size())
        {
            if(candidates[idx] != candidates[idx-1])
            {
                allCombToSum(candidates, ans, comb, idx, target);
                break;
            }
            idx++;
        }
    }
    
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) 
    {
        sort(candidates.begin(), candidates.end());
        vector<vector<int>> ans;
        vector<int> comb;
        allCombToSum(candidates, ans, comb, 0, target);
        return ans;
    }
};
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