523. Continuous Subarray Sum

Given a list of non-negative numbersand a target integer k, write a function to check if the arrayhas a continuous subarray of size at least 2 that sums up to the multiple of k,that is, sums up to n*k where n is also an integer.

Example 1:

Input: [23, 2, 4, 6,7],  k=6

Output: True

Explanation: Because [2,4] is a continuous subarray of size 2 and sums up to 6.

Example 2:

Input: [23, 2, 6, 4,7],  k=6

Output: True

Explanation: Because [23,2, 6, 4, 7] is an continuous subarray of size 5 and sums up to 42.

public class Solution {    public boolean checkSubarraySum(int[] nums, int k) {        if(nums == null || nums.length == 0 || nums.length == 1){            return false;        }        Map<Integer, Integer> map = new HashMap<Integer, Integer>(){{put(0,-1);}};;        int sum = 0;        for(int i=0; i<nums.length; i++){            sum += nums[i];            if(k != 0){                sum %= k;            }            if(!map.containsKey(sum)){                map.put(sum, i); //把余数都存下来，如果之前碰到这个余数，那么这个区间就是要求的            }else{                if(i - map.get(sum) > 1){                    return true;                }            }        }        return false;    }}