✅200. 岛屿数量 about like-algorithms HOT 2 OPEN

/**
 * @param {character[][]} grid
 * @return {number}
 */
var numIslands = function (grid) {
    let count = 0;
    function dfs(row, col) {
        if (
            row < 0 ||
            row >= grid.length ||
            col < 0 ||
            col >= grid[0].length ||
            grid[row][col] === "0"
        ) {
            return;
        }
        grid[row][col] = "0";
        dfs(row + 1, col);
        dfs(row - 1, col);
        dfs(row, col + 1);
        dfs(row, col - 1);
    }
    for (let row = 0; row < grid.length; row++) {
        for (let col = 0; col < grid[0].length; col++) {
            if (grid[row][col] === "1") {
                count++;
                dfs(row, col);
            }
        }
    }
    return count;
};

function helper(grid, x, y, rowLen, colLen) {
    if (x < 0 || y < 0 || x > rowLen - 1 || y > colLen - 1 || grid[x][y] == '0') return;

    grid[x][y] = '0';

    helper(grid, x - 1, y, rowLen, colLen);
    helper(grid, x + 1, y, rowLen, colLen);
    helper(grid, x, y - 1, rowLen, colLen);
    helper(grid, x, y + 1, rowLen, colLen);
}
/**
 * @param {character[][]} grid
 * @return {number}
 */
var numIslands = function(grid) {
    // DFS
    let isLand = 0;
    const rowLen = grid.length;
    if (rowLen === 0) return 0;
    const colLen = grid[0].length;

    for (let x = 0; x < rowLen; x++) {
        for (let y = 0; y < colLen; y++) {
            if (grid[x][y] == '1') {
                helper(grid, x, y, rowLen, colLen);
                isLand++;
            }
        }
    }

    return isLand;
};