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40. Combination Sum II

Array Backtracking

Problem - Combination Sum II

Medium

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

Solutions

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class Solution:
    def combinationSum2(self, candidates: List[int], target: int) -> List[List[int]]:
        def dfs(i: int, sum_val: int):
            if sum_val == 0:
                results.append(tmp[:])
            if i >= len(candidates) or sum_val < candidates[i]:
                return
            for j in range(i, len(candidates)):
                if j > i and candidates[j] == candidates[j - 1]:
                    continue
                tmp.append(candidates[j])
                dfs(j + 1, sum_val - candidates[j])
                tmp.pop()

        candidates.sort()
        results = []
        tmp = []

        dfs(0, target)

        return results

Submission Stats:

  • Runtime: 7 ms (72.27%)
  • Memory: 17.7 MB (84.14%)