HDU1043BFS 康托展开 八数码

经典的八数码问题

至于康托展开，百度知道。。。

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <cmath>#include <queue>using namespace std;int jc[11] = {1,1,2,6,24,120,720,5040,40320,362880};bool vis[444444];string path[444444];int aim;int mx[4] = {0,0,1,-1};int my[4] = {1,-1,0,0};char direction[4] = {'l','r','u','d'};struct State{    int x,y;    int s[11];    int state;    string path;};char mp[4][4];bool in(State a){    if(a.x >= 0 && a.x < 3 && a.y >= 0 && a.y < 3)        return true;    else        return false;}int contor(int s[]){    int sum = 0;    for(int i = 0 ; i < 9 ; i ++){        int num = 0;        for(int j = i + 1 ; j < 9 ; j ++){            if(s[j] < s[i]){                num++;            }        }        sum += num*jc[9-i-1];    }    return sum + 1;}queue<State> q;void BFS(){    memset(vis,0,sizeof(vis));    State s;    for(int i = 0 ; i < 8 ; i ++){        s.s[i] = i+1;    }    s.s[8] = 0;    s.state = contor(s.s);    s.x = 2;    s.y = 2;    s.path = "";    path[s.state] = "";    vis[s.state] = 1;    q.push(s);    while(!q.empty()){        State cnt = q.front();        q.pop();        for(int i = 0 ; i < 4 ; i ++){            State nt = cnt;            nt.x = cnt.x + mx[i];            nt.y = cnt.y + my[i];            if(in(nt) == 0)                continue;            nt.s[cnt.x*3+cnt.y] = nt.s[nt.x*3+nt.y];            nt.s[nt.x*3+nt.y] = 0;            nt.state = contor(nt.s);            if(vis[nt.state] == 0){                path[nt.state] = direction[i]+nt.path;                nt.path = path[nt.state];                vis[nt.state] = 1;                q.push(nt);            }        }    }}int main(){    char str;    State now;    BFS();    while(cin>>str){        if(str == 'x'){            now.x = 0;            now.y = 0;            now.s[0] = 0;        }        else            now.s[0] = str - '0';        for(int i = 1 ; i < 9 ; i ++){            cin>>str;            if(str == 'x'){                now.x = i/3;                now.y = i%3;                now.s[i] = 0;            }            else                now.s[i] = str-'0';        }        now.state = contor(now.s);        if(vis[now.state] == 1)            cout<<path[now.state]<<endl;        else            cout<<"unsolvable"<<endl;    }    return 0;}