hdu 5012 Dice(西安网络赛F题,BFS)

BFS+记忆化搜索。。

网赛的时候，竟然一开始没发现这道水题。后来TYQ做的时候用了很久去判断一开始就是INF的情况，其实就这道题的数据而言，根本不需要。。。

后来在hdu上交的时候，限制搜索步长为3，竟然都AC了。。。

不过，就是这么水的数据，我一开始误打的DFS竟然WA了！！

代码先注释了，等哪天空了来对拍一下 = = Orz。。

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <vector>
#include <queue>
#include <stack>
#include <cassert>
#include <algorithm>
#include <cmath>
#include <set>
#include <map>
#include <limits>

using namespace std;

#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define F(i, n) for (int (i)=0;(i)<(n);++(i))
#define REP(i, s, t) for(int (i)=(s);(i)<=(t);++(i))
#define UREP(i, s, t) for(int (i)=(s);(i)>=(t);--(i))
#define REPOK(i, s, t, o) for(int (i)=(s);(i)<=(t) && (o);++(i))
#define MEM0(addr, size) memset(addr, 0, size)
#define LBIT(x) x&-x

#define PI 3.1415926535897932384626433832795
#define HALF_PI 1.5707963267948966192313216916398

#define MAXN 100
#define MAXM 10000
#define MOD 10000007

typedef long long LL;

const double maxdouble = numeric_limits<double>::max();
const double eps = 1e-10;
const int INF = 0x7FFFFFFF;

#define DEBUG

map<int, int> _map;
int buf[MAXN];
int ans = INF;

struct Dice{
int top;
int bot;
int lef;
int rig;
int fro;
int bac;
bool read_in() {
return scanf("%d %d %d %d %d %d",&top, &bot, &lef, &rig, &fro, &bac) != EOF;
}
int make_num() {
int ret = top;
ret = ret*10 + bot;
ret = ret*10 + lef;
ret = ret*10 + rig;
ret = ret*10 + fro;
ret = ret*10 + bac;
return ret;
}
bool operator == (Dice & b) {
return top == b.top && bot == b.bot && lef == b.lef && rig == b.rig
&& fro == b.fro && bac == b.bac;
}
};

Dice A, B;
int cnt[4];

Dice left_rotation(const Dice & d) {
Dice ret = d;
int tmp = ret.top;
ret.top = ret.rig;
ret.rig = ret.bot;
ret.bot = ret.lef;
ret.lef = tmp;
return ret;
}

Dice right_rotation(const Dice & d) {
Dice ret = d;
int tmp = ret.top;
ret.top = ret.lef;
ret.lef = ret.bot;
ret.bot = ret.rig;
ret.rig = tmp;
return ret;
}

Dice front_rotation(const Dice & d) {
Dice ret = d;
int tmp = ret.top;
ret.top = ret.bac;
ret.bac = ret.bot;
ret.bot = ret.fro;
ret.fro = tmp;
return ret;
}

Dice back_rotation(const Dice & d) {
Dice ret = d;
int tmp = ret.top;
ret.top = ret.fro;
ret.fro = ret.bot;
ret.bot = ret.bac;
ret.bac = tmp;
return ret;
}
/*
int dfs(Dice & d, int step) {
if (d == A) {
ans = min(ans, step);
return 0;
}
Dice tmp;
int now = d.make_num(), num, val = INF;
if (_map.find(now) != _map.end())
return _map[now];
// left
if (cnt[0] < 4) {
tmp = left_rotation(d);
num = tmp.make_num();
if (_map.find(num) != _map.end()) {
int n = _map[num];
if (n != INF)
val = min(val, n);
} else {
++cnt[0];
val = min(val, dfs(tmp, step+1));
--cnt[0];
}
}
// right
if (cnt[1] < 4) {
tmp = right_rotation(d);
num = tmp.make_num();
if (_map.find(num) != _map.end()) {
int n = _map[num];
if (n != INF)
val = min(val, n);
} else {
++cnt[1];
val = min(val, dfs(tmp, step+1));
--cnt[1];
}
}
// front
if (cnt[2] < 4) {
tmp = front_rotation(d);
num = tmp.make_num();
if (_map.find(num) != _map.end()) {
int n = _map[num];
if (n != INF)
val = min(val, n);
} else {
++cnt[2];
val = min(val, dfs(tmp, step+1));
--cnt[2];
}
}
// bottom
if (cnt[3] < 4) {
tmp = back_rotation(d);
num = tmp.make_num();
if (_map.find(num) != _map.end()) {
int n = _map[num];
if (n != INF)
val = min(val, n);
} else {
++cnt[3];
val = min(val, dfs(tmp, step+1));
--cnt[3];
}
}

if (val == INF)
_map[now] = INF;
else {
_map[now] = val+1;
ans = min(ans, step+val+1);
}
return _map[now];
}*/

int main() {
freopen("input.in", "r", stdin);

while(A.read_in() && B.read_in()) {
ans = INF;
_map.clear();
queue<Dice> q;
//memset(cnt, 0, sizeof(cnt));
//dfs(B, 0);
q.push(B);
_map[B.make_num()] = 0;

while(q.empty() == false) {
Dice fr = q.front();q.pop();
int num = fr.make_num();
int step = _map[num];
if (fr == A) {
ans = min(ans, step);
break;
}
//cout << "front: " << num << " step: " << step <<  endl;
if (step > 9)
continue;
Dice t;
// left
t = left_rotation(fr);
num = t.make_num();
if (_map.find(num) == _map.end()) {
q.push(t);_map[num] = step+1;
}

// right
t = right_rotation(fr);
num = t.make_num();
if (_map.find(num) == _map.end()) {
q.push(t);_map[num] = step+1;
}
// front
t = front_rotation(fr);
num = t.make_num();
if (_map.find(num) == _map.end()) {
q.push(t);_map[t.make_num()] = step+1;
}
// back
t = back_rotation(fr);
num = t.make_num();
if (_map.find(num) == _map.end()) {
q.push(t);_map[t.make_num()] = step+1;
}
}

if (ans == INF)
printf("-1\n");
else
printf("%d\n", ans);
}

return 0;
}