leetcode 解题记录 --- 40. Combination Sum II

第一版本代码：

class Solution(object):
    def combinationSum2(self, candidates, target):
        """
        :type candidates: List[int]
        :type target: int
        :rtype: List[List[int]]
        """
        candidates.sort()
        self.ans = []
        vis = [0 for i in range(len(candidates))]
        self.dfs(candidates,[],vis,0,target)

        return  self.ans

    def dfs(self,nums,tem,vis,start,target):
        if target==0 and tem not in self.ans:
            self.ans.append(tem.copy())
            return
        if target<0:
            return
        for i in range(start,len(nums)):
                if nums[i]>target:
                    break
                if vis[i]==0:
                    tem.append(nums[i])
                    vis[i] = 1
                    self.dfs(nums,tem,vis,i,target-nums[i])
                    tem.pop()
                    vis[i]=0

用vis来判断是否使用

并且没有一个很好的去重方法

第二版本：

class Solution(object):
    def combinationSum2(self, candidates, target):
        """
        :type candidates: List[int]
        :type target: int
        :rtype: List[List[int]]
        """
        candidates.sort()
        self.ans = []

        self.dfs(candidates,[],0,target)

        return  self.ans

    def dfs(self,nums,tem,start,target):
        if target==0 :
            self.ans.append(tem.copy())
            return
        if target<0:
            return
        for i in range(start,len(nums)):
                if nums[i]>target:
                    break
                if i>start and nums[i]==nums[i-1]:
                    continue
                tem.append(nums[i])
                self.dfs(nums,tem,i+1,target-nums[i])
                tem.pop()

用start = i+1 来控制只使用一次，因为[i+1:]都是没有使用过的

去重：这个很有技巧性，学会来

if i>0 and nums[i]==nums[i-1] continue

if i>start and nums[i]==nums[i-1] continue

样例 [1,1,6,6]

 

来源：CSDN

作者：不知道你在说什么

链接：https://blog.csdn.net/a870735654/article/details/103237424