小红开锁

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std::pair<int , int> indx[4] = {{0,1} ,{1 , 0},{0,-1} , {-1 ,0}} ;
int n ;
void modify(int x , std::vector<std::vector<char>> &g) {

	std::pair<int , int> pre = {x , x} , now = {x, x + 1} ;
	char p = g[x][x] ;
	int k = 0 ;
	while ( now.first != x || now.second != x ) {
		swap(p , g[now.first][now.second]) ;
		int nx = now.first + indx[k].first , ny = now.second + indx[k].second ;
		if ( nx < x || nx > 2 * n - x + 1 || ny < x || ny > 2 * n - x + 1 ) k = (k + 1) % 4 ;
		nx = now.first + indx[k].first , ny = now.second + indx[k].second ;
		now = {nx , ny} ;
	} 
	swap(p, g[x][x]) ;
}
bool check(int x,int y,std::vector<std::vector<char>> &g) {

	if ( y == 1 ) {
		for(int i = x ; i <= n ; ++ i) if (g[i][x] != 'X' || g[x][i] != 'X') return false ;
	} else if ( y == 2 ) {
		for(int i = x , j = 2 * n - x + 1 ; i <= n ; ++ i , -- j) if (g[i][2 * n - x + 1] != 'X' || g[x][j] != 'X' ) return false ;
	} else if ( y == 3 ) {
		for(int i = 2 * n - x + 1 , j = 2 * n - x + 1 ; i > n ; -- i , -- j) if ( g[i][2 * n - x + 1] != 'X' || g[2 * n - x + 1][j] != 'X') return false ;
	} else {
		for(int i = 2 * n - x + 1 , j = x ; i > n ; -- i , ++ j) if (g[i][x] != 'X' || g[2 * n - x + 1][j] != 'X') return false ;
	}
	return true ;
}

void solve()
{
	cin >> n ;

	std::vector<std::vector<char> > g(2 * n + 1 , std::vector<char> (2 * n + 1 ,'O'));

	for(int i = 1 ; i <= 2 * n ; ++ i) {
		string str ;
		cin >> str ;
		for(int j = 1 ; j <= 2 * n ; ++ j) 
		{
			g[i][j] = str[j - 1] ;
		}
	}
	int ans = inf ;  
	for(int k = 1 ; k <= 4 ; ++ k) {
		auto a = g ;
		int num = 0 ;
		for(int i = 1 ; i <= n ; ++ i) {
			while ( !check(i , k , a) ) {
				++ num ;
				modify(i , a) ;
			}
		}	
		ans = min(ans , num) ;	
	}
	cout << ans << '\n' ;
}