Solution130.java

package backstracking_problem;


/**
 * floodfill 洪水填充算法——深度优先遍历
 */
public class Solution130 {

    int[][] d = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
    int m , n;

    public void solve(char[][] board) {

        if (board == null || board.length == 0) {
            return;
        }

        m = board.length;
        n = board[0].length;

        for (int i = 0; i < m; i++) {
            dfs(board, i, 0);
            dfs(board, i, n - 1);
        }

        for (int i = 0; i < n; i++) {
            dfs(board, 0, i);
            dfs(board, m - 1, i);
        }

        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (board[i][j] == 'T') {
                    board[i][j] = 'O';
                } else if (board[i][j] == 'O') {
                    board[i][j] = 'X';
                }
            }
        }
    }

    private void dfs(char[][] board, int i, int j) {
        if (i < 0 || i >= m || j < 0 || j >= n || board[i][j] != 'O') {
            return;
        }
        board[i][j] = 'T';
        for (int[] d : d) {
            dfs(board, i + d[0], j + d[1]);
        }
    }

}