【POJ 1753】Flip Game

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【POJ 1753】Flip Game

二进制+(BFS)暴力枚举

原本用二位字符数组存发现遍历困难并且翻动棋子也难办后来想到一维线性
下标 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
在图中即为
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
预处理出一个数组进行翻转后来又发现预处理难办灵光一现由于只有黑白两色可用1 0标记看到1 0想到的当然就是二进制了并且又做成了个线性刚好16位二进制一切迎刃而解翻转可用二进制运算^(异或) 上代码

#include <cstdio>#include <cstdlib>#include <cstring>#include <queue>#define INF 0x3f3f3f3fusing namespace std;int ms;int step[65536];int dir[32];bool vis[65536];int tp;int GetNum(char *str)//黑1 白 0{    int i,x = 0;    for(i = 1; i <= 16; ++i)    {        x <<= 1;        x += (str[i] == 'b')? 1: 0;    }    return x;}//void PrintNum(int x)//{//    int i = 1;//    while(x)//    {//        if(x&1) printf("1 ");//        else printf("0 ");//        x >>= 1;//        if(!(i%4)) printf("\n");//        ++i;//    }//    for(; i <= 16; ++i)//    {//        printf("0 ");//        if(!(i%4)) printf("\n");//    }//    printf("\n\n");//}void Memset(char *str,char a){    int i,j;    for(i = 1; i <= 16; ++i)            str[i] = a;}void Getdir(){    tp = 0;    char str[49];    int i,j;    Memset(str,'w');    for(i = 16; i >= 1; --i)    {        str[i+1] = str[i+5] = str[i+2]= 'w';        if(i-3 > 0) str[i-3] = 'w';        str[i] = str[i+4] = 'b';        if(i%4) str[i+1] = 'b';        if((i-1)%4) str[i-1] = 'b';        if(i-4 > 0) str[i-4] = 'b';        dir[tp++] = GetNum(str);    }}void Bfs(){    memset(step,INF,sizeof(step));    memset(vis,0,sizeof(vis));    step[ms] = 0;    int i,x,v;    queue <int> q;    q.push(ms);    while(!q.empty())    {        x = q.front();        q.pop();        vis[x] = 0;        for(i = 0; i < tp; ++i)        {            v = x^dir[i];            if(step[v] > step[x]+1)            {                step[v] = step[x]+1;                if(!vis[v])                {                    q.push(v);                    vis[v] = 1;                }            }        }    }}int main(){    //freopen("in.txt","r",stdin);    char str[18];    int i,j,x;    for(i = 1; i < 17; i += 4)    {        scanf("%s",str+i);    }    ms = GetNum(str);    Getdir();//    for(i = 0; i < tp; ++i)//        PrintNum(dir[i]);    if(ms == 0 || ms == 65535) printf("0\n");    else    {        Bfs();        x = min(step[0],step[65535]);        if(x == INF) printf("Impossible\n");        else printf("%d\n",x);    }    return 0;}

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