翻转快——搜索+贪心

http://poj.org/problem?id=3279

一般都玩过的游戏

翻转快，一块砖块翻开，其他周围四块跟它自己变的颜色相反

如果直接搜索的话，2^(15*15)铁定超时了

其实只要枚举2^15第一行，然后在此基础上贪心

即第一行为map[1][j]==1,下面也为 1

#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string.h>
#include<cmath>
using namespace std;

int n,m,ret=0;
bool s[19];
bool map[19][19];
bool tmap[19][19];
bool hash[19][19];
bool r[19][19];

int main()
{
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        int add=0;
        int i,j,k,ok=0;
        for(i=1;i<=n;i++){
            for(j=1;j<=m;j++){
                scanf("%d",&map[i][j]);
                tmap[i][j]=map[i][j];
                if(map[i][j]==1)
                {
                    ok=1;
                    add++;
                }
            }
        }
        
        if(ok==0){
            for(i=1;i<=n;i++){
                printf("%d",map[i][1]);
                for(j=2;j<=m;j++){
                    printf(" %d",map[i][j]);
                }
                printf("\n");
            }
            continue;
        }
        
        memset(hash,0,sizeof(hash));
        
        int max=9999,count=0,dui,all=0;
        int N=(int)pow(2*1.0,m*1.0);
        for(k=0;k<N;k++)
        {
            memset(hash,0,sizeof(hash));
            memset(s,0,sizeof(s));
            
            count=0;
            for(i=1;i<=n;i++){
                for(j=1;j<=m;j++){
                    map[i][j]=tmap[i][j];
                }
            }
            
            j=m;
            int temp=k;
            while(temp){
                if(temp%2==1){
                    s[j]=1;
                }
                temp=temp/2;
                j--;
            }
            
            i=1;
            for(j=1;j<=m;j++){
                if(s[j]==1)
                {
                    hash[i][j]=1;
                    count++;
                    map[i][j]=map[i][j]^1;
                    map[i][j+1]=map[i][j+1]^1;
                    map[i+1][j]=map[i+1][j]^1;
                    map[i][j-1]=map[i][j-1]^1;
                }
            }
            
            for(i=1;i<n;i++){
                for(j=1;j<=m;j++){
                    if(map[i][j]==1)
                    {
                        hash[i+1][j]=1;
                        count++;
                        map[i+1][j]=map[i+1][j]^1;
                        map[i][j]=map[i][j]^1;
                        map[i+1][j-1]=map[i+1][j-1]^1;
                        map[i+2][j]=map[i+2][j]^1;
                        map[i+1][j+1]=map[i+1][j+1]^1;
                    }
                }
            }
            
            dui=0;
            for(i=1;i<=n;i++){
                for(j=1;j<=m;j++){
                    if(map[i][j]==1)
                    {
                        dui=1;
                        break;
                    }
                }
            }
            
            if(dui==0)
                if(count<max)
                {
                    all=1;
                    for(i=1;i<=n;i++){
                        for(j=1;j<=m;j++){
                            r[i][j]=hash[i][j];
                        }
                    }
                    max=count;
                }
        }
        
        if(all==0){
            printf("IMPOSSIBLE\n");
            continue;
        }
        
        for(i=1;i<=n;i++){
            printf("%d",r[i][1]);
            for(j=2;j<=m;j++){
                printf(" %d",r[i][j]);
            }
            printf("\n");
        }
    }
    return 0;
}