class Solution {
    int[][] dirs = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };    // 四个方向，上下左右
    
    public int numEnclaves(int[][] A) {
        int ans = 0;

        for (int row = 0; row < A.length; row++) {
            for (int col = 0; col < A[0].length; col++) {
                // 当在边界且边界这里是陆地（即1）的时候，往下深搜，把连接到这块陆地的所有陆地转化为半岛（-1）
                if (isBoundary(A, row, col) && A[row][col] == 1) {
                    dfs(A, row, col);
                }
            }
        }
        
        // 计算岛屿的面积
        for (int row = 0; row < A.length; row++)
            for (int col = 0; col < A[0].length; col++)
                if(A[row][col] == 1) ans++;
        return ans;
    }
    
    
    private void dfs(int[][] A, int row, int col) {
        // 超出地图边界或者非陆地或者已经遍历过的陆地，直接返回
        if (outOfBoundary(A, row, col) || A[row][col] == 0 || A[row][col] == -1) return;
        // 将该陆地标记为岛屿，并遍历
        A[row][col] = -1;
        for (int[] dir : dirs) {
            dfs(A, row + dir[0], col + dir[1]);
        }
    }
    
    // 判断地图边界
    private boolean isBoundary(int[][] A, int row, int col) {
        return row == 0 || row == A.length - 1 || col == 0 || col == A[0].length - 1;
    }
    
    // 判断是否超出地图边界
    private boolean outOfBoundary(int[][] A, int row, int col) {
        return row < 0 || row > A.length - 1 || col < 0 || col > A[0].length - 1;
    }
    
}