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Copy pathsurroundedRegions.cpp
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235 lines (205 loc) · 5.39 KB
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// Source : https://oj.leetcode.com/problems/surrounded-regions/
// Author : Hao Chen
// Date : 2014-10-12
/**********************************************************************************
*
* 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.
*
* For example,
*
* X X X X
* X O O X
* X X O X
* X O X X
*
* After running your function, the board should be:
*
* X X X X
* X X X X
* X X X X
* X O X X
*
*
**********************************************************************************/
#include <stdlib.h>
#include <time.h>
#include <iostream>
#include <vector>
#include <queue>
using namespace std;
void print(vector< vector<char> > &board);
//Runtime Error for 250 x 250 matrix
void markOpen(vector< vector<char> > &board, int row, int col, int r, int c) {
if (board[r][c] == 'O'){
board[r][c]='N'; // 'N' means it's not closed
if (r < row-1) {
markOpen(board, row, col, r+1, c);
}
if (r > 0) {
markOpen(board, row, col, r-1, c);
}
if (c < col-1 ) {
markOpen(board, row, col, r, c+1);
}
if (c>0) {
markOpen(board, row, col, r, c-1);
}
}
}
//Runtime Error for 250 x 250 matrix
void solve_recursively(vector< vector<char> > &board) {
if (board.size()<=0 || board[0].size()<=0) return;
int row = board.size();
int col = board[0].size();
//left & right edge
for (int r=0; r<row; r++){
if ( board[r][0] == 'O') {
markOpen(board, row, col, r, 0);
}
if ( board[r][col-1] == 'O') {
markOpen(board, row, col, r, col-1);
}
}
//top & bottom edge
for (int c=1; c<col-1; c++){
if ( board[0][c] == 'O') {
markOpen(board, row, col, 0, c);
}
if ( board[row-1][c] == 'O') {
markOpen(board, row, col, row-1, c);
}
}
print(board);
// change 'N' to 'O', change 'O' to 'X'
for (int r=0; r<row; r++) {
for (int c=0; c<col; c++) {
if (board[r][c] == 'O') {
board[r][c]='X';
} else if (board[r][c] == 'N') {
board[r][c]='O';
}
}
}
}
/*change the recursive method to non_recursive way by using queue*/
struct position{
int row, col;
void set(int r, int c) { row = r; col = c; }
position(int r, int c): row(r), col(c) {}
};
void solve_non_recursively(vector< vector<char> > &board) {
if (board.size()<=0 || board[0].size()<=0) return;
int row = board.size();
int col = board[0].size();
queue<position> q;
position p(0,0);
//left & right edge
for (int r=0; r<row; r++){
if ( board[r][0] == 'O') {
board[r][0] = 'N';
p.set(r, 0);
q.push(p) ;
}
if ( board[r][col-1] == 'O') {
board[r][col-1] = 'N';
p.set(r, col-1);
q.push(p) ;
}
}
//top & bottom edge
for (int c=1; c<col-1; c++){
if ( board[0][c] == 'O') {
board[0][c] = 'N';
p.set(0, c);
q.push(p) ;
}
if ( board[row-1][c] == 'O') {
board[row-1][c] = 'N';
p.set(row-1, c);
q.push(p) ;
}
}
while (!q.empty()){
p = q.front();
q.pop();
int r = p.row;
int c = p.col;
if (r < row-1 && board[r+1][c] == 'O') {
board[r+1][c] = 'N';
p.set(r+1, c);
q.push(p);
}
if (r > 0 && board[r-1][c] == 'O') {
board[r-1][c] = 'N';
p.set(r-1, c);
q.push(p);
}
if (c < col-1 && board[r][c+1] == 'O') {
board[r][c+1] = 'N';
p.set(r, c+1);
q.push(p);
}
if (c>0 && board[r][c-1] == 'O') {
board[r][c-1] = 'N';
p.set(r, c-1);
q.push(p);
}
}
print(board);
// change 'N' to 'O', change 'O' to 'X'
for (int r=0; r<row; r++) {
for (int c=0; c<col; c++) {
if (board[r][c] == 'O') {
board[r][c]='X';
} else if (board[r][c] == 'N') {
board[r][c]='O';
}
}
}
}
void solve(vector< vector<char> > &board) {
//Runtime Error for 250 x 250 matrix
/* solve_recursively(board); */
solve_non_recursively(board);
}
void construct(vector< vector<char> > &board, int row, int col) {
srand(time(0));
for(int i=0; i<row; i++){
vector<char> line;
for(int j=0; j<col; j++){
if (i==0 || j==0 || i==row-1 || j==col-1)
line.push_back(rand()%3 ? 'X' : 'O');
else
line.push_back(rand()%2 ? 'X' : 'O');
}
board.push_back(line);
}
}
void print(vector< vector<char> > &board) {
for(int i=0; i<board.size(); i++){
for(int j=0; j<board[i].size(); j++){
cout << board[i][j] << " ";
}
cout << endl;
}
cout << endl;
}
int main(int argc, char** argv )
{
int row, col;
row = col = 6;
if (argc>1){
row = atoi(argv[1]);
}
if (argc>2){
col = atoi(argv[2]);
}
vector< vector<char> > data;
construct(data, row, col);
print(data);
solve(data);
print(data);
return 0;
}