Leetcode 3392 count subarrays of length three with a condition

3392. Count Subarrays of Length Three With a Condition

Given an integer array nums, return the number of subarrays of length 3 such that the sum of the first and third numbers equals exactly half of the second number.

A subarray is a contiguous non-empty sequence of elements within an array.

Example 1:

Input: nums = [1,2,1,4,1]

Output: 1

Explanation:

Only the subarray [1,4,1] contains exactly 3 elements where the sum of the first and third numbers equals half the middle number.

Example 2:

Input: nums = [1,1,1]

Output: 0

Explanation:

[1,1,1] is the only subarray of length 3. However, its first and third numbers do not add to half the middle number.

Constraints:

• 3 <= nums.length <= 100
• -100 <= nums[i] <= 100

Solution 1

java

class Solution {
    public int countSubarrays(int[] nums) {
        int result = 0;
        for (int i = 0; i < nums.length - 2; i++) {
            if (2 * (nums[i] + nums[i + 2]) == nums[i + 1]) {
                result++;
            }
        }
        return result;
    }
}