MostFrequentNumberFollowingKeyInArray.php

<?php

namespace App;

/**
 * Most Frequent Number Following Key In an Array
 *
 * You are given a 0-indexed integer array nums. You are also given an integer key, which is present in nums. For every
 * unique integer target in nums, count the number of times target immediately follows an occurrence of key in nums. In
 * other words, count the number of indices i such that:
 *  - 0 <= i <= nums.length - 2,
 *  - nums[i] == key and,
 *  - nums[i + 1] == target.
 * Return the target with the maximum count. The test cases will be generated such that the target with maximum count
 * is unique.
 * Example 1:
 * Input: nums = [1,100,200,1,100], key = 1
 * Output: 100
 * Explanation: For target = 100, there are 2 occurrences at indices 1 and 4 which follow an occurrence of key.
 * No other integers follow an occurrence of key, so we return 100.
 *
 * Example 2:
 * Input: nums = [2,2,2,2,3], key = 2
 * Output: 2
 * Explanation: For target = 2, there are 3 occurrences at indices 1, 2, and 3 which follow an occurrence of key.
 * For target = 3, there is only one occurrence at index 4 which follows an occurrence of key.
 * target = 2 has the maximum number of occurrences following an occurrence of key, so we return 2.
 *
 * https://leetcode.com/problems/most-frequent-number-following-key-in-an-array
 */
class MostFrequentNumberFollowingKeyInArray
{
    /**
     * @param int[] $nums
     * @param int $key
     * @return int
     */
    public function mostFrequent(array $nums, int $key): int
    {
        $mp = array();
        $maxi = PHP_INT_MIN;
        $maxvalue = 0;

        for ($i = 0; $i < count($nums) - 1; $i++) {
            if ($nums[$i] === $key) {
                if (!isset($mp[$nums[$i + 1]])) {
                    $mp[$nums[$i + 1]] = 1;
                } else {
                    $mp[$nums[$i + 1]]++;
                }

                if ($maxi < $mp[$nums[$i + 1]]) {
                    $maxi = $mp[$nums[$i + 1]];
                    $maxvalue = $nums[$i + 1];
                }
            }
        }

        return $maxvalue;
    }
}