文章作者:Tyan
博客:noahsnail.com | CSDN |
1. Description
2. Solution
class Solution {
public:
void solve(vector>& board) {
if(board.size() == 0) {
return;
}
int rows = board.size();
int columns = board[0].size();
flipBorder(board, 'O', '1', rows, columns);
for(int i = 1; i < rows - 1; i++) {
for(int j = 1; j < columns - 1; j++) {
if(board[i][j] == 'O') {
capture(board, i, j, rows, columns, 'O', 'X');
}
}
}
flipBorder(board, '1', 'O', rows, columns);
}
private:
void flipBorder(vector>& board, char src, char target, int& rows, int& columns) {
for(int i = 0; i < rows; i++) {
if(board[i][0] == src) {
capture(board, i, 0, rows, columns, src, target);
}
if(board[i][columns - 1] == src) {
capture(board, i, columns - 1, rows, columns, src, target);
}
}
for(int i = 0; i < columns; i++) {
if(board[0][i] == src) {
capture(board, 0, i, rows, columns, src, target);
}
if(board[rows - 1][i] == src) {
capture(board, rows - 1, i, rows, columns, src, target);
}
}
}
void capture(vector>& board, int i, int j, int& rows, int& columns, char src, char target) {
if(i < 0 || i == rows || j < 0 || j == columns || board[i][j] != src) {
return;
}
board[i][j] = target;
capture(board, i + 1, j, rows, columns, src, target);
capture(board, i - 1, j, rows, columns, src, target);
capture(board, i, j + 1, rows, columns, src, target);
capture(board, i, j - 1, rows, columns, src, target);
}
};
Reference
- https://leetcode.com/problems/surrounded-regions/description/