从小白开始刷算法 dfs篇 leetcode.200

// 仅是我的思路代码，leetcode上大神更厉害
class Solution {
    public int numIslands(char[][] grid) {
        //获取行数
        int row = grid.length;
        //获取列数
        int col = grid[0].length;
        int res = 0;
        for (int i = 0; i < row; i++) {
            for (int j = 0; j < col; j++) {
                if (grid[i][j] == '1') {
                    res++;
                    dfs(grid, i, j, row, col);
                }
            }
        }
        return res;
    }
    public void dfs(char[][] grid, int x, int y, int row, int col) {
        //边界条件判断
        if (x < 0 || y < 0 || x >= row || y >= col || grid[x][y] == '0') {
            return;
        }
        grid[x][y] = '0';
        dfs(grid, x + 1, y, row, col);
        dfs(grid, x - 1, y, row, col);
        dfs(grid, x, y + 1, row, col);
        dfs(grid, x, y - 1, row, col);
    }
}

class Solution {
    public int numIslands(char[][] grid) {
        int row = grid.length;
        int col = grid[0].length;
        int count = 0;
        // 创建一个队列用于存储待访问的位置
        Queue<int[]> queue = new LinkedList<>();
        // 遍历整个网格
        for (int i = 0; i < row; i++) {
            for (int j = 0; j < col; j++) {
                if (grid[i][j] == '1') {
                    // 找到一个岛屿，将其标记为已访问，并加入队列
                    count++;
                    bfs(grid, row, col, queue, i, j);
                }
            }
        }
        return count;
    }
    private void bfs(char[][] grid, int row, int col, Queue<int[]> queue, int i, int j) {
        grid[i][j] = '0';
        queue.offer(new int[]{i, j});
        // 开始进行广度优先搜索
        while (!queue.isEmpty()) {
            int[] curr = queue.poll();
            int x = curr[0];
            int y = curr[1];
            if (x - 1 >= 0 && grid[x - 1][y] == '1') {
                queue.add(new int[]{x - 1, y});
                grid[x - 1][y] = '0';
            }
            if (y - 1 >= 0 && grid[x][y - 1] == '1') {
                queue.add(new int[]{x, y - 1});
                grid[x][y - 1] = '0';
            }
            if (x + 1 < row && grid[x + 1][y] == '1') {
                queue.add(new int[]{x + 1, y});
                grid[x + 1][y] = '0';
            }
            if (y + 1 < col && grid[x][y + 1] == '1') {
                queue.add(new int[]{x, y + 1});
                grid[x][y + 1] = '0';
            }
        }
    }
}