HDU 1043 eight (Astar 八数码)

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#include<vector>
#include<cmath>
#include<map>
#include<string>

using namespace std;
struct Node
{
int maze[3][3];
int h, g;
int x, y;
int Hash;
bool operator<(const Node n1)const
{
return h != n1.h ? h>n1.h:g>n1.g;
}
bool check()
{
if (x >= 0 && x<3 && y >= 0 && y<3)
return true;
return false;
}
} s, u, v, tt;
int HASH[9] = { 1,1,2,6,24,120,720,5040,40320 };
int destination = 322560;
int vis[400000];
int pre[400000];
int way[4][2] = { { 0,1 },{ 0,-1 },{ 1,0 },{ -1,0 } };
int get_hash(Node tmp)
{
int a[9], k = 0;
for (int i = 0; i<3; i++)
for (int j = 0; j<3; j++)
a[k++] = tmp.maze[i][j];
int res = 0;
for (int i = 0; i<9; i++)
{
int k = 0;
for (int j = 0; j<i; j++)
if (a[j]>a[i])
k++;
res += HASH[i] * k;
}
return res;
}
bool isok(Node tmp)
{
int a[9], k = 0;
for (int i = 0; i<3; i++)
for (int j = 0; j<3; j++)
a[k++] = tmp.maze[i][j];
int sum = 0;
for (int i = 0; i<9; i++)
for (int j = i + 1; j<9; j++)
if (a[j] && a[i] && a[i]>a[j])
sum++;
return !(sum & 1);
}
int get_h(Node tmp)
{
int ans = 0;
for (int i = 0; i<3; i++)
for (int j = 0; j<3; j++)
if (tmp.maze[i][j])
ans += abs(i - (tmp.maze[i][j] - 1) / 3) + abs(j - (tmp.maze[i][j] - 1) % 3);
return ans;
}
void astar()
{
priority_queue<Node>que;
que.push(s);
while (!que.empty())
{
u = que.top();
que.pop();
for (int i = 0; i<4; i++)
{
v = u;
v.x += way[i][0];
v.y += way[i][1];
if (v.check())
{
swap(v.maze[v.x][v.y], v.maze[u.x][u.y]);
v.Hash = get_hash(v);
if (vis[v.Hash] == -1 && isok(v))
{
vis[v.Hash] = i;
v.g++;
pre[v.Hash] = u.Hash;
v.h = get_h(v);
que.push(v);
}
if (v.Hash == destination)
return;
}
}
}
}
void print()
{
string ans;
ans.clear();
int nxt = destination;
while (pre[nxt] != -1)
{
switch (vis[nxt])
{
case 0:
ans += 'r';
break;
case 1:
ans += 'l';
break;
case 2:
ans += 'd';
break;
case 3:
ans += 'u';
break;
}
nxt = pre[nxt];
}
for (int i = ans.size() - 1; i >= 0; i--)
putchar(ans[i]);
puts("");
}
int main()
{
std::ios::sync_with_stdio(false);
std::cin.tie(0);
string str;
while (getline(cin,str))
{
int k = 0;
memset(vis, -1, sizeof(vis));
memset(pre, -1, sizeof(pre));
for (int i = 0; i<3; i++)
for (int j = 0; j<3; j++)
{
if ((str[k] <= '9'&&str[k] >= '0') || str[k] == 'x')
{
if (str[k] == 'x')
{
s.maze[i][j] = 0;
s.x = i;
s.y = j;
}
else
s.maze[i][j] = str[k] - '0';
}
else
j--;
k++;
}
if (!isok(s))
{
printf("unsolvable\n");
continue;
}
s.Hash = get_hash(s);
if (s.Hash == destination)
{
puts("");
continue;
}
vis[s.Hash] = -2;
s.g = 0;
s.h = get_h(s);
astar();
print();
}
return 0;
}