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40. Combination Sum II

Difficulty Topics

Description

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

Solution

combination-sum-ii.py
class Solution:
    def combinationSum2(self, candidates: List[int], target: int) -> List[List[int]]:
        n = len(candidates)
        res = []
        candidates.sort()

        def dfs(target, index, path):
            if target < 0: return

            if target == 0:
                res.append(path)
                return

            for i in range(index, n):
                if i > index and candidates[i] == candidates[i - 1]: continue
                dfs(target - candidates[i], i + 1, path + [candidates[i]])

        dfs(target, 0, [])

        return res