You are given two positive integer arrays spells and potions, of length n and m respectively, where spells[i] represents the strength of the ith spell and potions[j] represents the strength of the jth potion. You are also given an integer success. A

successfulPairs.js

/**
 * @param {number[]} spells
 * @param {number[]} potions
 * @param {number} success
 * @return {number[]}
 */

// Helper function to preprocess potions using a suffix-style bucket sort
var suffixBucketSort = function(potions) {
    // Find the maximum potion value to size the result array
    let maxPotion = Math.max(...potions);

    // Create an array of size (maxPotion + 1) initialized with zeros
    let res = new Array(maxPotion + 1);
    for (let i = 0; i <= maxPotion; i++) {
        res[i] = 0;
    }

    // Count the frequency of each potion strength
    for (let potion of potions) {
        ++res[potion];
    }

    // Convert frequency array into a suffix sum array
    // res[i] will represent the number of potions ≥ i
    for (let i = maxPotion - 1; i >= 0; i--) {
        res[i] += res[i + 1];
    }

    // Return the suffix sum array
    return res;
};

// Main function to compute the number of successful pairs
var successfulPairs = function(spells, potions, success) {
    // Preprocess potions into a suffix bucket array
    let bucket = suffixBucketSort(potions);

    // Prepare result array to store the count of successful pairs for each spell
    let res = new Array(spells.length);

    for (let i = 0; i < spells.length; i++) {
        let spell = spells[i];

        // Calculate the minimum potion strength needed for a successful pair
        // success / spell gives the threshold potion value
        // Math.ceil ensures we round up to meet or exceed the success threshold
        res[i] = bucket[Math.ceil(success / spell)] || 0;
        // If the threshold is higher than any potion, fallback to 0
    }

    // Return the array of successful pair counts
    return res;
};