LeetCode-in-Java

974. Subarray Sums Divisible by K

Medium

Given an integer array nums and an integer k, return the number of non-empty subarrays that have a sum divisible by k.

A subarray is a contiguous part of an array.

Example 1:

Input: nums = [4,5,0,-2,-3,1], k = 5

Output: 7

Explanation:

There are 7 subarrays with a sum divisible by k = 5:

[4, 5, 0, -2, -3, 1], [5], [5, 0], [5, 0, -2, -3], [0], [0, -2, -3], [-2, -3]

Example 2:

Input: nums = [5], k = 9

Output: 0

Constraints:

• 1 <= nums.length <= 3 * 104
• -104 <= nums[i] <= 104
• 2 <= k <= 104

Solution

public class Solution {
    public int subarraysDivByK(int[] nums, int k) {
        int[] map = new int[k];
        int ans = 0;
        int sum = 0;
        map[0] = 1;
        for (int num : nums) {
            sum += num;
            int temp = sum % k;
            if (temp < 0) {
                temp += k;
            }
            ans += map[temp]++;
        }
        return ans;
    }
}

This site is open source. Improve this page.