LeetCode 523. Continuous Subarray Sum

Question

Given an integer array nums and an integer k, return true if nums has a continuous subarray of size at least two whose elements sum up to a multiple of k, or false otherwise.

An integer x is a multiple of k if there exists an integer n such that x = n * k. 0 is always a multiple of k.

https://leetcode.com/problems/continuous-subarray-sum/

• Solution1

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

Complexity:

Time complexity: O( n)

Space complexity: O(n)