[LeetCode] Combinations Sum 2

문제

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.

예제

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]
]

조건

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

답

풀이 1

백트래킹 방식으로 해결하였다. 합이 타겟보다 큰 순간 가지치기를 한다.

class Solution:
    def combinationSum2(self, candidates: List[int], target: int) -> List[List[int]]:

        if sum(candidates) < target:
            return []
        ans = []
        sub = []
        def dfs(index, csum):
            if csum == target:
                if not sorted(sub) in ans:
                    ans.append(sorted(sub))
                return
            
            for i in range(index, len(candidates)):
                if csum + candidates[i] > target:
                    continue
                sub.append(candidates[i])
                dfs(i+1, csum+candidates[i])
                sub.pop()
        
        dfs(0, 0)
        return ans