hdu 1043 Eight(BFS经典)

//#include<bits/stdc++.h>
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <vector>
#include <queue>
#include <stack>
#include <cassert>
#include <algorithm>
#include <cmath>
#include <climits>
#include <set>
#include <map>
using namespace std;

#define SPEED_UP iostream::sync_with_stdio(false);
#define FIXED_FLOAT cout.setf(ios::fixed, ios::floatfield);
#define rep(i, s, t) for(int (i)=(s);(i)<=(t);++(i))
#define urep(i, s, t) for(int (i)=(s);(i)>=(t);--(i))

typedef long long LL;

const int Maxn = 3;
const int dx[] = {-1, 1, 0, 0};
const int dy[] = {0, 0, -1, 1};

int n=3, m=3;
char mm[9];
int tab[11], last[362880+100], sav[362880+100], spos;

struct st{
char s[9];
int t, h, pos;
st(){};
st(const char *m, int t, int h, int pos):t(t), h(h), pos(pos) {
memcpy(s, m, 9);
}
};
st q[362880+100];

bool init() {
memset(last, -1, sizeof(last));
char ch;
rep(i, 0, 8) {
if (scanf("%c", &ch) == 1) {
if (ch == 'x')
mm[i] = '9', spos = i;
else
mm[i] = ch;
}
else
return false;
getchar();
}
return true;
}

int Hash(const char* a, int len) {
int ret = 0;
rep(i, 0, len-1) {
int t = 0;
rep(j, i+1, len-1)
if (a[j] < a[i]) ++t;
ret += tab[len-1-i]*t;
}
return ret;
}

void print_state(const st &x) {
cout << endl;
rep(i, 0, 2) {
rep(j, 0, 2) cout << x.s[i*3+j];
cout << endl;
}
cout << "t: " << x.t << " pos: " << x.pos << endl;
}

void print(int x) {
if (last[x] == -1 || last[x] == -2) return;
print(last[x]);
switch(sav[x]) {
case 0:putchar('u');break;
case 1:putchar('d');break;
case 2:putchar('l');break;
case 3:putchar('r');break;
}
}

int check(const char* p) {
rep(i, '1', '9')
if (i != (*p++)) return 0;
return 1;
}

void solve() {
int x, y, nx, ny, npos;
int hcode = Hash(mm, 9);
q[0] = st(mm, 0, hcode, spos);
last[hcode] = -2;
int head = 0, tail = 1;
while (head < tail) {
const st &fr = q[head++];
int h = fr.h;
//print_state(fr);
if (check(fr.s)) {
//cout << fr.t << endl;
print(h);
cout << endl;
return;
}

x = fr.pos/3,  y = fr.pos%3;
rep(i, 0, 3) {
nx = x + dx[i];
ny = y + dy[i];
npos = nx*3+ny;
if (0 <= nx && nx < 3 && 0 <= ny && ny < 3) {
st &tmp = q[tail];
tmp = fr;
swap(tmp.s[fr.pos], tmp.s[npos]);
int _h = Hash(tmp.s, 9);
if (last[_h] != -1) continue;

tmp.t += 1;
tmp.h = _h;
tmp.pos = npos;
++tail;
sav[_h] = i;
last[_h] = h;
}
}
}

puts("unsolvable");
}

int main() {
#ifndef ONLINE_JUDGE
freopen("input.in", "r", stdin);
#endif
//SPEED_UP
tab[0] = 1;rep(i, 1, 9) tab[i] = tab[i-1]*i;

while (init()) {
solve();
}

return 0;
}