leetCode-深度优先遍历

岛屿数量

深度优先遍历

class Solution {
    public int numIslands(char[][] grid) {
        int xlen = grid[0].length;
        int ylen = grid.length;
        int count = 0;

        for (int x = 0; x < xlen; x++) {
            for (int y = 0; y < ylen; y++) {
                if (grid[y][x] == '1') {
                    dfs(grid, y, x);
                    count++;
                }
            }
        }

        return count;
    }

    private void dfs(char[][] grid, int y, int x) {
        if (y < 0 || y >= grid.length)
            return;
        if (x < 0 || x >= grid[0].length)
            return;
        if (grid[y][x] == '0')
            return;

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

        int[] dx = { 0, 0, 1, -1 };
        int[] dy = { 1, -1, 0, 0 };

        for (int i = 0; i < 4; i++) {
            dfs(grid, y + dy[i], x + dx[i]);
        }
    }

}