LeetCode [523] Continuous Subarray Sum

Given a list of non-negative numbers and a target integer k, write a function to check if the array has 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.

Note:

1. The length of the array won't exceed 10,000.
2. You may assume the sum of all the numbers is in the range of a signed 32-bit integer.

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class Solution { public boolean checkSubarraySum(int[] nums, int k) { Map<Integer, Integer> map = new HashMap<>(); map.put(0,-1); int s = 0, n = nums.length; for(int i=0; i<n; ++i){ s += nums[i]; int r = s%k; if(map.containsKey(r)){ int j = map.get(r); if(i-j>=2) return true; }else{ map.put(r, i); } } return false; } }