14：Flip Game

#include<iostream>
#include<string>
using namespace std;
int a[5][5];int b[5][5];
#define rep(i,j,k) for(int i=j;i<=k;i++)
int n=4;
string s[20];
void update(int i,int j)
{
    b[i][j]=1-b[i][j];
    b[i-1][j]=1-b[i-1][j];
    b[i+1][j]=1-b[i+1][j];
    b[i][j-1]=1-b[i][j-1];
    b[i][j+1]=1-b[i][j+1];
}
int judge(int x,int flag)
{
    rep(i,1,n) rep(j,1,n) b[i][j]=a[i][j];
    int sum=0;
    rep(i,1,n)
    {
        if(x%2)
        {
            update(1,i);
            sum++;
        }
        x/=2;
    }
    rep(i,1,n-1)
    rep(j,1,n)
    {
        if(b[i][j]==flag)
        {
            update(i+1,j);
            sum++;
        }
    }
    rep(i,1,n)
    if(b[n][i]==flag)
    return 300;
    return sum;
}
int main()
{
    rep(i,1,n)
    {
        string tmp;
        cin>>tmp;
        s[i]=" "+tmp;
    }
    rep(i,1,n)
    {
        rep(j,1,n)
        if(s[i][j]=='w')
        a[i][j]=0;
        else
        a[i][j]=1;
    }
    int maxnum=300;
    rep(i,0,(1<<n)-1)
    {
        maxnum=min(maxnum,judge(i,1));
        maxnum=min(maxnum,judge(i,0));
    }
    if(maxnum==300) cout<<"Impossible";
    else cout<<maxnum;
}