3349. Adjacent Increasing Subarrays Detection I

Description

Given an array nums of n integers and an integer k, determine whether there exist two adjacent of length k such that both subarrays are strictly increasing. Specifically, check if there are two subarrays starting at indices a and b (a < b), where:

• Both subarrays nums[a..a + k - 1] and nums[b..b + k - 1] are strictly increasing.
• The subarrays must be adjacent, meaning b = a + k.

Return true if it is possible to find two such subarrays, and false otherwise.

 

Example 1:

Input: nums = [2,5,7,8,9,2,3,4,3,1], k = 3

Output: true

Explanation:

• The subarray starting at index 2 is [7, 8, 9], which is strictly increasing.
• The subarray starting at index 5 is [2, 3, 4], which is also strictly increasing.
• These two subarrays are adjacent, so the result is true.

Example 2:

Input: nums = [1,2,3,4,4,4,4,5,6,7], k = 5

Output: false

 

Constraints:

• 2 <= nums.length <= 100
• 1 < 2 * k <= nums.length
• -1000 <= nums[i] <= 1000

 

Solutions

Solution: Greedy

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

 

JavaScript

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {boolean}
 */
const hasIncreasingSubarrays = function (nums, k) {
  const n = nums.length;
  let increasing = 1;
  let prevIncreasing = 0;

  for (let index = 1; index < n; index++) {
    if (nums[index] > nums[index - 1]) {
      increasing += 1;
    } else {
      prevIncreasing = increasing;
      increasing = 1;
    }

    if (increasing >= k * 2 || Math.min(prevIncreasing, increasing) >= k) {
      return true;
    }
  }

  return false;
};