LeetCode 2765: Longest Alternating Subarray Solution

Master LeetCode problem 2765 (Longest Alternating Subarray), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2765. Longest Alternating Subarray

Easy

Array Enumeration

Problem Explanation

Explanation:

To solve this problem, we can iterate through the input array and check if the current element, the previous element, and their difference follow the alternating pattern. If they do, we increase the length of the current alternating subarray. If the pattern is broken, we update the maximum length found so far and reset the current length. Finally, we return the maximum length found.

Start with a current length of 2 (minimum length for alternating subarrays).
Iterate through the input array from the second element.
Check if the current element, the previous element, and their difference follow the alternating pattern.
If they do, increment the current length.
If the pattern is broken, update the maximum length found so far and reset the current length.
Return the maximum length found.

Time complexity: O(n) Space complexity: O(1)

Solution Code

class Solution {
    public int maxAlternatingSubarray(int[] nums) {
        int n = nums.length;
        int maxLen = -1;
        int curLen = 2;
        
        for (int i = 2; i < n; i++) {
            if ((nums[i] - nums[i - 1]) * (nums[i - 1] - nums[i - 2]) < 0) {
                curLen++;
            } else {
                maxLen = Math.max(maxLen, curLen);
                curLen = 2;
            }
        }
        
        return Math.max(maxLen, curLen);
    }
}

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