Leetcode: 200. Number of Islands

count_island_dfs_array.php

<?php 
function numIslands(array $grid):int {
    $length      = count($grid);
    $islandCount = 0;

    if ($length === 0) {
        return 0;
    }

    for ($i = 0; $i < $length; $i++) {
        $jCount = count($grid[$i]);
        for ($j = 0; $j < $jCount; $j++) {

            if ($grid[$i][$j] === '1') {
                $islandCount++;
                dfs($grid, $i, $j);
            }
        }
    }

    return $islandCount;
}

function dfs(array &$grid, int $i, int $j): void {
    $iLength = count($grid);
    $jLength = count($grid[0] ?? []);

    if ($i < 0 || $j < 0 || $i >= $iLength || $j >= $jLength || $grid[$i][$j] === '0') {
        return;
    }

    $grid[$i][$j] = '0';
    dfs($grid, $i - 1, $j);
    dfs($grid, $i + 1, $j);
    dfs($grid, $i, $j - 1);
    dfs($grid, $i, $j + 1);
}