2962. Count Subarrays Where Max Element Appears at Least K Times

Description

You are given an integer array nums and a positive integer k.

Return the number of subarrays where the maximum element of nums appears at leastk times in that subarray.

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

 

Example 1:

Input: nums = [1,3,2,3,3], k = 2
Output: 6
Explanation: The subarrays that contain the element 3 at least 2 times are: [1,3,2,3], [1,3,2,3,3], [3,2,3], [3,2,3,3], [2,3,3] and [3,3].

Example 2:

Input: nums = [1,4,2,1], k = 3
Output: 0
Explanation: No subarray contains the element 4 at least 3 times.

 

Constraints:

• 1 <= nums.length <= 105
• 1 <= nums[i] <= 106
• 1 <= k <= 105

 

Solutions

Solution: Sliding Window

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

 

JavaScript

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number}
 */
const countSubarrays = function (nums, k) {
  const n = nums.length;
  const maxNum = Math.max(...nums);
  let left = 0;
  let count = 0;
  let result = 0;

  for (let index = 0; index < n; index++) {
    if (nums[index] === maxNum) {
      count += 1;
    }

    while (count >= k) {
      if (nums[left] === maxNum) {
        count -= 1;
      }

      result += n - index;
      left += 1;
    }
  }

  return result;
};