记录编号	288284	评测结果	AAAAAAAAAAAAAAAAAAAA
题目名称	[NOIP 2010冲刺七]翻转游戏	最终得分	100
用户昵称	天爷爷眉头紧皱意识到名字并不好起	是否通过	通过
代码语言	C++	运行时间	0.004 s
提交时间	2016-08-02 19:39:23	内存使用	0.31 MiB

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cstdlib>
#include<queue>
using namespace std;
char map[6][6];
int h[6][6],a[6][6],tot;
void Change(int x,int y){
	h[x][y]=!h[x][y];
	if(x>=1&&y-1>=1)h[x][y-1]=!h[x][y-1];
	if(x-1>=1&&y>=1)h[x-1][y]=!h[x-1][y];
	if(x+1<=4&&y<=4)h[x+1][y]=!h[x+1][y];
	if(x<=4&&y+1<=4)h[x][y+1]=!h[x][y+1];
}
void Clean(){
	for(int i=1;i<=4;i++)
		for(int j=1;j<=4;j++)
			h[i][j]=a[i][j];
}
bool judge(){
	int cnt=0;
	for(int i=1;i<=4;i++)
		for(int j=1;j<=4;j++)if(h[i][j]==1)cnt++;
	if(cnt==16||cnt==0)return true;
	else return false;
}
int Work2(int a,int w){
	int ret=0;
	if(w==1)Clean();
	for(int i=1;i<=4;i++)
		if(h[1][i]!=a){
			Change(2,i);ret++;
		}
	for(int i=1;i<=4;i++)
		if(h[2][i]!=a){
			Change(3,i);ret++;
		}
	for(int i=1;i<=4;i++)
		if(h[3][i]!=a){
			Change(4,i);ret++;
		}
	if(judge())return ret;
	return 99999999;
}
int Work1(int a){
	int ret=0,ans=99999999;
	Clean();
	ret=0;
	Change(1,1),ret++,ret+=Work2(a,0);
	if(ret>=99999999)ret=99999999;
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,2),ret++,ret+=Work2(a,0);
	if(ret>=99999999)ret=99999999;
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,3),ret++,ret+=Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,4),ret++,ret+=Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,1),Change(1,2),ret+=2,ret+=Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,1),Change(1,3),ret+=2,ret+=Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,1),Change(1,4),ret+=2,ret+=Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,2),Change(1,3),ret+=2,ret+=Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,2),Change(1,4),ret+=2,ret+=Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,3),Change(1,4),ret+=2,ret+=Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,1),Change(1,2),Change(1,3),ret+=3+Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,1),Change(1,2),Change(1,4),ret+=3+Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,2),Change(1,3),Change(1,4),ret+=3+Work2(a,0);
	ans=min(ret,ans);

	Clean();
	ret=0;
	Change(1,1),Change(1,2),Change(1,3),Change(1,4),ret+=4+Work2(a,0);
	ans=min(ret,ans);
	Clean();

	if(ans>=99999999)return 99999999+1;
	else return ans;
}
int main(){
	freopen("flip.in","r",stdin);freopen("flip.out","w",stdout);
	for(int i=1;i<=4;i++)
		for(int j=1;j<=4;j++){
			cin>>map[i][j];
			if(map[i][j]=='w')tot++,a[i][j]=1;
			else a[i][j]=0;
		}
	if(tot==16||tot==0){
		puts("0");
		return 0;
	}
	int ans=min(min(min(Work1(0),Work1(1)),Work2(0,1)),Work2(1,1));
	if(ans>=99999999)puts("Impossible");
	else cout<<ans;
	return 0;
}