【路飞】 200. 岛屿数量 js实现

上题目：

给你一个由 '1'（陆地）和 '0'（水）组成的的二维网格，请你计算网格中岛屿的数量。

岛屿总是被水包围，并且每座岛屿只能由水平方向和/或竖直方向上相邻的陆地连接形成。

此外，你可以假设该网格的四条边均被水包围。

示例 1：

输入：grid = [ ["1","1","1","1","0"], ["1","1","0","1","0"], ["1","1","0","0","0"], ["0","0","0","0","0"] ] 输出：1 示例 2：

输入：grid = [ ["1","1","0","0","0"], ["1","1","0","0","0"], ["0","0","1","0","0"], ["0","0","0","1","1"] ] 输出：3  

提示：

m == grid.length n == grid[i].length 1 <= m, n <= 300

解题：

/**
 * @param {character[][]} grid
 * @return {number}
 */
var numIslands = function(grid) {
    let res = 0;
    let rows = grid.length;
    if (rows === 0) return 0;
    let cols = grid[0].length;

    for (let i=0; i<rows; i++) {
        for (let j=0; j<cols; j++) {
            if (grid[i][j] === '1') {
                res++;
                search(i,j);
            }
        }
    }

    function search(i, j) {
        if (i < 0 || j < 0 || i >= rows || j >= cols || grid[i][j] === '0' || grid[i][j] === '#') return;

        grid[i][j] = '#';

        search(i+1, j);
        search(i-1, j);
        search(i, j+1);
        search(i, j-1);
    }

    return res;
};