本文介绍了一种解决二维棋盘中被'X'包围的'O'区域捕获问题的算法。通过深度优先搜索（DFS）标记边界上的'O'避免误判，最终将未被标记的'O'转化为'X'。
题目
Given a 2D board containing'X'and'O',capture all regions surrounded by'X'.
A region is captured by flipping all'O'sinto'X's in that surrounded region .
For example,
X X X X
X O O X
X X O X
X O X X
After running your function, the boardshould be:
X X X X
X X X X
X X X X
X O X X
实现
public class Main22 {
publicint rowNum = 0;
publicint colNum = 0;
publicvoid solve(char[][] board) {
if(board == null || board.length <= 0 || board[0].length <= 0) {
return;
}
rowNum= board.length;
colNum= board[0].length;
for(int i = 0; i < colNum; i++) {
dfs(board,0, i);
dfs(board,rowNum - 1, i);
}
for(int i = 0; i < rowNum; i++) {
dfs(board,i, 0);
dfs(board,i, colNum - 1);
}
for(int i = 0; i < rowNum; i++) {
for(int j = 0; j < colNum; j++) {
if(board[i][j] == 'O') {
board[i][j]= 'X';
}
}
}
for(int i = 0; i < rowNum; i++) {
for(int j = 0; j < colNum; j++) {
if(board[i][j] == '*') {
board[i][j]= 'O';
}
}
}
}
privatevoid dfs(char[][] board, int row, int col) {
if(board[row][col] == 'O') {
board[row][col]= '*';
if(row > 1) {
dfs(board,row - 1, col);
}
if(col > 1) {
dfs(board,row, col - 1);
}
if(row < rowNum - 1) {
dfs(board,row + 1, col);
}
if(col < colNum - 1) {
dfs(board,row, col + 1);
}
}
}
}
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