poj2965 The Pilots Brothers' refrigerator

2017-10-5

解答

直接枚举即可

代码

#include<iostream>using namespace std;const int N = 4;char x[N+1][N+1],y[N+1][N+1];int z[N+1][N+1];int s;bool f=false;void set(int p,int q){    for (int i=1;i<=N;i++){        if (x[i][q]=='-') x[i][q]='+';        else x[i][q]='-';        if (x[p][i]=='-') x[p][i]='+';        else x[p][i]='-';    }    if (x[p][q]=='+') x[p][q]='-';    else x[p][q]='+';}void init(){    int i,j;    for (i=1;i<=N;i++){        for (j=1;j<=N;j++){            x[i][j]=y[i][j];        }    }}void show(){    int i,j;    cout<<s<<endl;    for (i=1;i<=N;i++){        for (j=1;j<=N;j++){            if (z[i][j]) cout<<i<<" "<<j<<endl;        }    }}bool res(){    int i,j;    s=0;    for (i=1;i<=N;i++){        for (j=1;j<=N;j++){            if (z[i][j]){                set(i,j);                s=s+1;            }        }    }    for (i=1;i<=N;i++){        for (j=1;j<=N;j++){            if (x[i][j]=='+') return false;        }    }    return true;}void dfs(int p,int q){    if (f) return ;    if (p==N+1){        if (res()){            f=true;            show();        }        init();        return ;    }    if (q==N+1){        dfs(p+1,1);        return ;    }    z[p][q]=1;    dfs(p,q+1);    z[p][q]=0;    dfs(p,q+1);}int main(){    int i,j;    for (i=1;i<=N;i++){        for (j=1;j<=N;j++){            cin>>x[i][j];            y[i][j]=x[i][j];        }    }    dfs(1,1);    return 0;}