POJ 2046 Gap 搜索- 状态压缩

题目地址： http://poj.org/problem?id=2046

一道搜索状态压缩的题目，关键是怎样hash。

AC代码：

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <list>
#include <deque>
#include <queue>
#include <iterator>
#include <stack>
#include <map>
#include <set>
#include <algorithm>
#include <cctype>
using namespace std;

typedef long long LL;
const int N=2222222;
const LL II=1000000007;
const int M=1000007;

struct xh
{
    int maps[4][8],step;
}w,e,vv[500000];

int aim[4][8]=//目标状态
{
    11,12,13,14,15,16,17,0,
    21,22,23,24,25,26,27,0,
    31,32,33,34,35,36,37,0,
    41,42,43,44,45,46,47,0
};

int s[80];
int vis[M];

int gethash(int t[][8])
{
    int i,j,k=0,hash=0;
    for(i=0;i<4;i++)
        for(j=0;j<8;j++)
        {
            s[k++]=t[i][j]/10;
            s[k++]=t[i][j]%10;
            //转化成数字，hash
        }
    for(i=0;i<k;i++)//hash
    {
        hash=hash*7+s[i];
    }
    hash=(hash&0x7fffffff)%M;
    return hash;
}

void chang(int num,int i,int j)
{
    int a,b;
    for(a=0;a<4;a++)
        for(b=1;b<8;b++)
        {
            if(w.maps[a][b]==num)
            {
                swap(w.maps[a][b],w.maps[i][j]);
                return ;
            }
        }
}

bool test(xh a)
{
    int i,j;
    for(i=0;i<4;i++)
        for(j=0;j<8;j++)
            if(a.maps[i][j]!=aim[i][j])
                return false;
    return true;
}

void bfs()
{
    int i,j,hash,head=0,tail=0;
    memset(vis,false,sizeof(vis));
    w.maps[0][0]=11;
    w.maps[1][0]=21;
    w.maps[2][0]=31;
    w.maps[3][0]=41;
    w.step=0;
    vv[tail++]=w;
    hash=gethash(w.maps);
    vis[hash]=true;
    while(head!=tail)
    {
        e=vv[head++];
        if(test(e))
        {
            printf("%d
",e.step);
            return ;
        }
        for(i=0;i<4;i++)
            for(j=1;j<8;j++)
            {
                w=e;
                if(w.maps[i][j]!=0)    continue;
                int num=w.maps[i][j-1];//前一个
                if(num==0||num==17||num==27||num==37||num==47)  continue;
                chang(num+1,i,j);
                hash=gethash(w.maps);
                if(!vis[hash])
                {
                    vis[hash]=true;
                    w.step++;
                    vv[tail++]=w;
                }
            }
    }
    printf("-1
");
}

int main()
{
    int i,j,T,k;
    cin>>T;
    while(T--)
    {
        memset(w.maps,0,sizeof(w.maps));
        for(i=0;i<4;i++)
            for(j=1;j<8;j++)
            {
                scanf("%d",&k);
                w.maps[i][j]=k;
                if(k==11||k==21||k==31||k==41)
                    w.maps[i][j]=0;
            }
        bfs();
    }
    return 0;
}