<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:
    def comboinationSum2Helper(self, candidates, target, path):
        if target < 0:
            return

        if target == 0:
            if path not in self.res:
                self.res.append(path)
            return

        if not candidates:
            return 

        for i in range(len(candidates)):
            if i != 0 and candidates[i] == candidates[i-1]:
                continue
            else:
                self.comboinationSum2Helper(candidates[i+1:], target - candidates[i], path + [candidates[i]])

    def combinationSum2(self, candidates: List[int], target: int) -> List[List[int]]:
        self.res = []
        candidates.sort()

        self.comboinationSum2Helper(candidates, target, [])

        return self.res

        
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