LeetCode 698 Partition to K Equal Sum Subsets

Given an array of integers nums and a positive integer k, find whether it's possible to divide this array into k non-empty subsets whose sums are all equal.

Example 1:

Input: nums = [4, 3, 2, 3, 5, 2, 1], k = 4
Output: True
Explanation: It's possible to divide it into 4 subsets (5), (1, 4), (2,3), (2,3) with equal sums.

 

Note:

• 1 <= k <= len(nums) <= 16.
• 0 < nums[i] < 10000.

这个题经历了多次超时终于A了。。。。。。。起因是我开始的基本法就是错的。放上代码：

class Solution(object):
    def canPartitionKSubsets(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: bool
        """
        nums = sorted(nums,reverse = True)
        if sum(nums)%k !=0 or max(nums) > sum(nums)/k:
            return False
        else:
            visited = [False for _ in range(len(nums))]
            cur_sum = sum(nums)/k
            return self.help(visited,cur_sum,sum(nums)/k,k,nums,0)
        
    def help(self,visited,cur_sum,target,k,nums,pos):
        if k == 1:
            return True
        if cur_sum == 0:
            return self.help(visited,target,target,k-1,nums,0)
        for i in range(pos,len(nums)):
            if not visited[i] and cur_sum>=nums[i]:
                visited[i] = True
                if self.help(visited,cur_sum-nums[i],target,k,nums,pos+1):
                    return True
                visited[i] = False
        return False