Leetcode 200. Number of Islands

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.

思路：碰见是1的点就进行宽度搜索，并把它的所有邻岛标记为0，总岛数+1.

public int numIslands(char[][] grid) {
    if (grid == null || grid.length == 0 || grid[0].length == 0) {
        return 0;
    }

    int res = 0;
    for (int i = 0; i < grid.length; i++) {
        for (int j = 0; j < grid[0].length; j++) {
            if (grid[i][j] == '1') {
                bfs(grid, i, j);
                res++;
            }
        }
    }

    return res;
}

private void bfs(char[][] grid, int i, int j) {
    int[] dx = {0, 1, 0, -1};
    int[] dy = {1, 0, -1, 0};
    Queue q = new LinkedList<>();
    int[] coor = {i, j};
    q.offer(coor);
    while (!q.isEmpty()) {
        int[] cur = q.poll();
        grid[cur[0]][cur[1]] = '0';
        for (int k = 0; k < 4; k++) {
            int tx = cur[0] + dx[k];
            int ty = cur[1] + dy[k];
            if (tx < 0 || tx >= grid.length || ty < 0 || ty >= grid[0].length || grid[tx][ty] == '0') {
                continue;
            }
            int[] neighbor = {tx, ty};
            q.offer(neighbor);
        }
    }
}