CheckIfNumberHasEqualDigitCountAndDigitValue.php

<?php

namespace App;

/**
 * Check if Number Has Equal Digit Count and Digit Value
 *
 * You are given a 0-indexed string num of length n consisting of digits. Return true if for every index i in the range
 * 0 <= i < n, the digit i occurs num[i] times in num, otherwise return false.
 *
 * Example 1:
 * Input: num = "1210"
 * Output: true
 * Explanation:
 * num[0] = '1'. The digit 0 occurs once in num.
 * num[1] = '2'. The digit 1 occurs twice in num.
 * num[2] = '1'. The digit 2 occurs once in num.
 * num[3] = '0'. The digit 3 occurs zero times in num.
 * The condition holds true for every index in "1210", so return true.
 *
 * Example 2:
 * Input: num = "030"
 * Output: false
 * Explanation:
 * num[0] = '0'. The digit 0 should occur zero times, but actually occurs twice in num.
 * num[1] = '3'. The digit 1 should occur three times, but actually occurs zero times in num.
 * num[2] = '0'. The digit 2 occurs zero times in num.
 * The indices 0 and 1 both violate the condition, so return false.
 *
 * https://leetcode.com/problems/check-if-number-has-equal-digit-count-and-digit-value
 */
class CheckIfNumberHasEqualDigitCountAndDigitValue
{
    /**
     * @param string $num
     * @return bool
     */
    public function digitCount(string $num): bool
    {
        $nums = str_split($num);
        foreach ($nums as $key => $val) {
            if (substr_count($num, "" . $key) !== (int)$val) {
                return false;
            }
        }
        return true;
    }
}