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.

判断平均值是否为整数，然后深度优先遍历，判断是否存在

class Solution {
    public boolean canPartitionKSubsets(int[] nums, int k) {//mytip
        //求平均值
        if(null==nums||0==nums.length||k<=0){
            return false;
        }
        int sum=0;
        for(int i = 0;i<nums.length;i++){
            sum+=nums[i];
        }
        if(sum%k!=0){
            return false;
        }
        boolean[] isVisit=new boolean[nums.length];
        return help(nums,isVisit,k,0,sum/k,0);
    }
    private boolean help(int[] nums,boolean[] isVisit,int k,int index,int avg,int curSum){
        if(k==0){
            return true;
        }
        if(curSum == avg){
            return help(nums,isVisit,k-1,0,avg,0);
        }
        for(int i = index;i<nums.length;i++){
            if(isVisit[i]){
                continue;
            }
            isVisit[i] = true;
            if(avg-curSum>=nums[i]&&help(nums,isVisit,k,i+1,avg,curSum+nums[i])){
                return true;
            }
            isVisit[i] = false;
        }
        return false;
    }
}