# My 12ms dfs c++

•     class Solution {
public:
void solve(vector<vector<char>>& board) {
int rows = board.size();
if(rows==0)
return;
int cols = board[0].size();
for(int i=0;i<rows;i++){
if(board[i][0]=='O'){
dfs(board,i,0);
}
if(board[i][cols-1]=='O')
dfs(board,i,cols-1);
}
for(int j=0;j<cols;j++){
if(board[0][j]=='O')
dfs(board,0,j);
if(board[rows-1][j]=='O')
dfs(board,rows-1,j);
}
for(int i=0;i<rows;i++){
for(int j=0;j<cols;j++){
if(board[i][j]=='Y')
board[i][j]='O';
else
board[i][j]='X';
}
}
}
void dfs(vector<vector<char>>& board, int x, int y){
int rows = board.size();
int cols = board[0].size();
board[x][y]='Y';
// cout<<x<<" "<<y<<endl;
int dir[4][2] = {0,1,1,0,0,-1,-1,0};
for(int i=0;i<4;i++){
int tx = x+dir[i][0];
int ty = y+dir[i][1];
while(tx>=0&&tx<rows&&ty>=0&&ty<cols&&board[tx][ty]=='O'){
board[tx][ty]='Y';
//cout<<tx<<" "<<ty<<endl;
for(int k=1;k<=3;k+=2){
int px = tx+dir[(i+k)%4][0];
int py = ty+dir[(i+k)%4][1];
if(px>=0&&px<rows&&py>=0&&py<cols&&board[px][py]=='O')dfs(board,px,py);

}
tx = tx+dir[i][0];
ty = ty+dir[i][1];
}
}
}
};

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