523. Continuous Subarray Sum

523. Continuous Subarray Sum

Medium

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.

Example 1:

• Input: nums = [23,2,4,6,7], k = 6
• Output: true
• Explanation: [2, 4] is a continuous subarray of size 2 whose elements sum up to 6.

Example 2:

• Input: nums = [23,2,6,4,7], k = 6
• Output: true
• Explanation: [23, 2, 6, 4, 7] is an continuous subarray of size 5 whose elements sum up to 42.

42 is a multiple of 6 because 42 = 7 * 6 and 7 is an integer.

Example 3:

• Input: nums = [23,2,6,4,7], k = 13
• Output: false

Constraints:

• 1 <= nums.length <= 105
• 0 <= nums[i] <= 109
• 0 <= sum(nums[i]) <= 231 - 1
• 1 <= k <= 231 - 1

Solution:

class Solution { /** * @param Integer[] $nums * @param Integer $k * @return Boolean */ function checkSubarraySum($nums, $k) { $prefixMod = 0; $modSeen = array(); $modSeen[0] = -1; for ($i = 0; $i < count($nums); $i++) { $prefixMod = ($prefixMod + $nums[$i]) % $k; if (array_key_exists($prefixMod, $modSeen)) { if ($i - $modSeen[$prefixMod] > 1) return 1; } else { $modSeen[$prefixMod] = $i; } } return 0; }
}

Contact Links