2. Surrounded Regions
Given a 2D board containing ‘X‘
and ‘O‘
, capture all regions surrounded by ‘X‘
.
A region is captured by flipping all ‘O‘
‘s into ‘X‘
‘s in that surrounded region.
Example
X X X X
X O O X
X X O X
X O X X
After capture all regions surrounded by ‘X‘
, the board should be:
X X X X
X X X X
X X X X
X O X X
写了一个dfs,过不来大数据测试
public class Solution { /** * @param board a 2D board containing ‘X‘ and ‘O‘ * @return void */ private boolean[][] visited; private int[] offset; private int m, n; public void surroundedRegions(char[][] board) { if (board == null || board.length == 0) { return; } // Write your code here m = board.length; n = board[0].length; int size = m * n; visited = new boolean[m][n]; offset = new int[] {0, 1, 0, -1, 0}; for (int i = 0; i < n; i++) { if (board[0][i] == ‘O‘ && visited[0][i] == false) { visited[0][i] = true; search(board, 0, i); } if (board[m - 1][i] == ‘O‘ && visited[m - 1][i] == false) { visited[m - 1][i] = true; search(board, m - 1, i); } } for (int i = 0; i < m; i++) { if (board[i][0] == ‘O‘ && visited[i][0] == false) { visited[i][0] = true; search(board, i, 0); } if (board[i][n - 1] == ‘O‘ && visited[i][n -1] == false) { visited[i][n - 1] = true; search(board, i, n - 1); } } for (int i = 1; i < m - 1; i++) { for (int j = 1; j < n - 1; j++) { if (board[i][j] == ‘O‘ && visited[i][j] == false) { board[i][j] = ‘X‘; } } } } private void search(char[][] board, int i, int j) { //System.out.println("debug " + i + " " + j); for (int k = 0; k < 4; k++) { int new_i = i + offset[k]; int new_j = j + offset[k + 1]; if (new_i < 0 || new_j < 0 || new_i >= m || new_j >= n) { continue; } if (visited[new_i][new_j] == false && board[new_i][new_j] == ‘O‘) { int index = i * n + j; int newIndex = new_i * n + j; visited[new_i][new_j] = true; search(board, new_i, new_j); } } } }
//to do BFSversion
时间: 2024-10-29 00:25:08