<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 combinationSum2(self, nums: List[int], target: int) -> List[List[int]]:
        nums.sort()
        n = len(nums)
        
        for i in range(n - 1, -1, -1):
            if nums[i] <= target:
                break
        
        nums, n = nums[:i+1], i + 1
        result = []
        self.findSum(result, nums, [], 0, n, target)
        return result

    def findSum(self, result: List[List[int]], nums: List[int], currentnums: List[int], i: int, n: int, target: int) -> None:
        if nums[i] > target:
            return

        target -= nums[i]
        currentnums.append(nums[i])
        if target == 0:
            result.append(copy.deepcopy(currentnums))
        elif i + 1 < n:
            self.findSum(result, nums, currentnums, i+1, n, target)
        
        target += nums[i]
        currentnums.pop()
        while i + 1 < n and nums[i+1] == nums[i]:
            i += 1
        
        if i + 1 < n:
            self.findSum(result, nums, currentnums, i+1, n, target)

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