'''
Given a collection of candidate numbers (candidates) and a target number (target), find all unique combinations in candidates where the candidate numbers sum to target.
Each number in candidates may only be used once in the combination.
Note: The solution set must not contain duplicate combinations.

Example 1:

Input: candidates = [10,1,2,7,6,1,5], target = 8
Output:
[
[1,1,6],
[1,2,5],
[1,7],
[2,6]
]

Example 2:

Input: candidates = [2,5,2,1,2], target = 5
Output:
[
[1,2,2],
[5]
]


Constraints:

1 <= candidates.length <= 100
1 <= candidates[i] <= 50
1 <= target <= 30
'''


def combination_sum(candidates, target):
    ans = []
    length = len(candidates)
    candidates.sort()

    def solve(index, nums, sum):
        if sum == target:
            ans.append(nums)
            return

        for i in range(index, length):
            if i > index and candidates[i] == candidates[i - 1]:
                continue

            if sum + candidates[i] > target:
                break

            solve(i + 1, nums + [candidates[i]], sum + candidates[i])

    solve(0, [], 0)
    return ans