Continuous Subarray Sum

Given an integer array nums and an integer k, return true if nums has a good subarray or false otherwise.

A good subarray is a subarray where:

• its length is at least two, and

• the sum of the elements of the subarray is a multiple of k.

Note that:

• A subarray is a contiguous part of the array.

• 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.

LeetCode Problem - 523

class Solution {
    public boolean checkSubarraySum(int[] nums, int k) {
        // Initialize a map to store the remainders and their indices
        Map<Integer, Integer> mp = new HashMap<>();
        // Add a base case to handle the case where the subarray starts at the beginning
        mp.put(0, -1);
        // Initialize a variable to keep track of the cumulative sum
        int sum = 0;

        // Iterate over the array
        for (int i = 0; i < nums.length; i++) {
            // Update the cumulative sum
            sum += nums[i];
            // Calculate the remainder of the sum divided by k
            int remainder = sum % k;
            // If the remainder is found in the map, check the subarray length
            if (mp.containsKey(remainder)) {
                // If the subarray length is greater than 1, return true
                if (i - mp.get(remainder) > 1) return true;
            } else {
                // If the remainder is not in the map, add it with the current index
                mp.put(remainder, i);
            }
        }
        // If no valid subarray is found, return false
        return false;
    }
}