HDU 1043 双向广搜 八数码 康托展开 逆序数

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<queue>
using namespace std;
char c;
int index[10] = {1,1,2,6,24,120,720,5040,40320};
int dir[4][2] = {1,0,-1,0,0,1,0,-1};
int vis[400000],found,state,father1[400000],father2[400000],move1[400000],move2[400000];
struct node
{
int state,loc;
char map[10];
}s1,s2;
queue<node>q1;
queue<node>q2;
int ct(char map[])
{
int ans = 0;
for(int i = 0; i < 9; i++)
{
int num = 0;
for(int j = i + 1; j < 9; j++)
{
if(map[i] > map[j]) num++;
}
ans += num * index[8 - i];
}
return ans;
}
void expend(queue<node> &q,int flag)
{
int x,y,xx,yy,k;
node cur,end;
cur = q.front();
q.pop();
k = cur.loc;
x = k / 3;
y = k % 3;
for(int i = 0; i < 4; i++)
{

xx = x + dir[i][0];
yy = y + dir[i][1];

if(xx >= 0 && yy >= 0 && xx < 3 && yy < 3)
{
end = cur;
end.loc = xx*3 + yy;
end.map[cur.loc] = cur.map[end.loc];
end.map[end.loc] = 9;
end.state = ct(end.map);
if(flag == 1 && vis[end.state] != 1)
{
move1[end.state] = i;
father1[end.state] = cur.state;
if(vis[end.state] == 2)
{
found = 1;
state = end.state;
return;
}
vis[end.state] = 1;
q.push(end);
}
else if(flag == 2 && vis[end.state] != 2)
{
move2[end.state] = i;
father2[end.state] = cur.state;
if(vis[end.state] == 1)
{
found = 1;
state = end.state;
return;
}
vis[end.state] = 2;
q.push(end);
}
}
}
}
int ReverseOrder(char map[])
{
int ans = 0;
for(int i = 0; i< 9; i++)
{
if(map[i] == 9) continue;
for(int j = i + 1; j < 9; j++)
{
if(map[j] == 9) continue;
if(map[i] > map[j]) ans++;
}
}
return ans;
}
void read()
{
int i = 0;
if(c == 'x')
{
s1.map[i++] = 9;
s1.loc = 0;
}
else if(c < '9' && '0' < c)
{
s1.map[i++] = c - '0';
}
while(scanf("%c",&c))
{
if(c == 'x')
{
s1.map[i++] = 9;
s1.loc = i - 1;
}
else if(c < '9' && '0' < c)
{
s1.map[i++] = c - '0';
}
if(i == 9) return;
}
}
void bfs2()
{
while(!q1.empty()) q1.pop();
while(!q2.empty()) q2.pop();
q1.push(s1);
q2.push(s2);
while(!q1.empty() || !q2.empty())
{
if(!q1.empty()) expend(q1,1);
if(found) return;
if(!q2.empty()) expend(q2,2);
if(found) return;
}
}
void path1(int st)
{
if(father1[st] != -1)
{
path1(father1[st]);
if(move1[st] == 0) printf("d");
else if(move1[st] == 1) printf("u");
else if(move1[st] == 2) printf("r");
else if(move1[st] == 3) printf("l");
}
return;
}
void path2(int st)
{
while(father2[st] != -1)
{
if(move2[st] == 0) printf("u");
else if(move2[st] == 1) printf("d");
else if(move2[st] == 2) printf("l");
else if(move2[st] == 3) printf("r");
st = father2[st];
}
}
int main()
{
//	freopen("t.txt","r",stdin);
int i;
while(~scanf(" %c",&c))
{
found = 0;
memset(vis,0,sizeof(vis));
if(c=='x')
{
s1.map[0]=9;
s1.loc=0;
}
else
s1.map[0]=c-'0';
for(i=1;i<9;i++)
{
scanf(" %c",&c);
if(c=='x')
{
s1.map[i]=9;
s1.loc=i;
}
else
s1.map[i]=c-'0';
}

s1.state = ct(s1.map);  vis[s1.state] = 1;  father1[s1.state] = -1;
if(s1.state == s2.state)
{
puts("");
continue;
}
if(ReverseOrder(s1.map) % 2 == 1)
{
printf("unsolvable\n");
continue;
}
for(i = 0; i < 9; i++)
{
s2.map[i] = i + 1;
}
s2.loc = 8;
s2.state = ct(s2.map);  vis[s2.state] = 2;  father2[s2.state] = -1;
bfs2();
if(found == 0)
{
printf("unsolvable\n");
continue;
}
path1(state);
path2(state);
printf("\n");

}
}