Given an integer array nums and an integer k, return the number of good subarrays of nums. A subarray arr is good if there are at least k pairs of indices (i, j) such that i < j and arr[i] == arr[j]. A subarray is a contiguous non-empty sequence of

countGood.js

/**
 * Function to count the number of "good" subarrays in an array.
 * A "good" subarray is defined as having at least `k` pairs of indices `(i, j)`
 * such that `nums[i] == nums[j]` and `i < j`.
 *
 * @param {number[]} nums - Array of integers to be evaluated.
 * @param {number} k - Minimum number of pairs needed to consider a subarray "good".
 * @return {number} - The total count of "good" subarrays.
 */
var countGood = function(nums, k) {
    const count = new Map(); // Map to store the frequency of elements in the current window.
    let left = 0; // Left pointer of the sliding window.
    let pairCount = 0; // Current count of pairs in the sliding window.
    let result = 0; // Result to store the total count of "good" subarrays.

    // Iterate through the array using the right pointer.
    for (let right = 0; right < nums.length; right++) {
        const val = nums[right]; // Current value at the right pointer.
        
        // Update the pair count based on the frequency of the current value.
        pairCount += count.get(val) || 0; 
        // Increment the frequency of the current value in the map.
        count.set(val, (count.get(val) || 0) + 1); 

        // While the number of pairs in the window meets or exceeds `k`,
        // adjust the left pointer and update the result.
        while (pairCount >= k) {
            // Add the number of valid subarrays ending at `right` to the result.
            result += nums.length - right; 
            const leftVal = nums[left]; // Value at the left pointer.
            
            // Decrement the frequency of the left value in the map.
            count.set(leftVal, count.get(leftVal) - 1); 
            // Update the pair count based on the reduced frequency.
            pairCount -= count.get(leftVal); 
            left++; // Move the left pointer forward to shrink the window.
        }
    }

    return result; // Return the total count of "good" subarrays.
};