bzoj 1054

一看就想到BFS。

由于状态只有2^16个，所以直接状压。

建议用宏定义优化代码。

#include<cstdio>
#include<cctype>
#include<algorithm>
#define t1 fr-(1<<i)+(1<<i+1)
#define t2 fr-(1<<i)+(1<<i-1)
#define t3 fr-(1<<i)+(1<<i+4)
#define t4 fr-(1<<i)+(1<<i-4)
using namespace std;
const int maxs=65536;
int read(){
    char c; while(!isdigit(c=getchar())); return c-'0';
}
int q[maxs],dis[maxs];
int main(){
    int s=0,t=0;
    for(int i=0;i<16;i+=1) s|=read()<<i;
    for(int i=0;i<16;i+=1) t|=read()<<i;
    int l=0,w=0;
    q[w++]=s; dis[s]=1;
    while(l<w && !dis[t]){
        int fr=q[l++];
        for(int i=0;i<16;i+=1)
            if(fr&(1<<i)){
                if(i%4!=3 && !(fr&(1<<i+1)) && !dis[t1]) dis[t1]=dis[fr]+1,q[w++]=t1;
                if(i%4 && !(fr&(1<<i-1)) && !dis[t2]) dis[t2]=dis[fr]+1,q[w++]=t2;
                if(i<=11 && !(fr&(1<<i+4)) && !dis[t3]) dis[t3]=dis[fr]+1,q[w++]=t3;
                if(i>=4 && !(fr&(1<<i-4)) && !dis[t4]) dis[t4]=dis[fr]+1,q[w++]=t4;
            }
    }
    printf("%d",dis[t]-1);
    return 0;
}