mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
111 lines
2.5 KiB
C++
111 lines
2.5 KiB
C++
#include<iostream>
|
|
#include<cstring>
|
|
#include<cstdio>
|
|
#include<queue>
|
|
#define N 40400
|
|
#define MAX 210
|
|
#define CNT 4000
|
|
using namespace std;
|
|
bool isprime[N];
|
|
int prime[CNT],cnt;
|
|
int map[MAX][MAX];
|
|
bool visited[MAX][MAX];
|
|
struct point{int x,y,step;};
|
|
void find_prime()
|
|
{
|
|
int i,j;
|
|
cnt=0;
|
|
memset(isprime,true,sizeof(isprime));
|
|
isprime[1]=false;
|
|
for(i=2;i<N;i++)
|
|
{
|
|
if(isprime[i])
|
|
{
|
|
prime[cnt++]=i;
|
|
for(j=2*i;j<N;j=j+i) isprime[j]=false;
|
|
}
|
|
}
|
|
}
|
|
void build_map(int p,int q,int s,int c)
|
|
{
|
|
if(s==0) return ;
|
|
int i;
|
|
for(i=q;i<q+c;i++) map[p][i]=s--;
|
|
for(i=p+1;i<p+c;i++) map[i][q+c-1]=s--;
|
|
for(i=q+c-2;i>q;i--) map[p+c-1][i]=s--;
|
|
for(i=p+c-1;i>p;i--) map[i][q]=s--;
|
|
build_map(p+1,q+1,s,c-2);
|
|
}
|
|
int t_i,t_j;
|
|
void find(int u)
|
|
{
|
|
int i,j;
|
|
for(i=1;i<=200;i++)
|
|
{
|
|
for(j=1;j<=200;j++)
|
|
{
|
|
if(u==map[i][j])
|
|
{
|
|
t_i=i;t_j=j;
|
|
return ;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
int BFS(int u,int v)
|
|
{
|
|
find(u);
|
|
point t,tt;
|
|
t.x=t_i;t.y=t_j;t.step=0;
|
|
queue<point>Q;
|
|
while(!Q.empty()) Q.pop();
|
|
Q.push(t);
|
|
visited[t.x][t.y]=true;
|
|
while(!Q.empty())
|
|
{
|
|
t=Q.front();Q.pop();
|
|
if(map[t.x][t.y]==v) return t.step;
|
|
if(t.x-1>=1&&!visited[t.x-1][t.y]&&!isprime[map[t.x-1][t.y]])
|
|
{
|
|
tt.x=t.x-1;tt.y=t.y;tt.step=t.step+1;
|
|
Q.push(tt);
|
|
visited[tt.x][tt.y]=true;
|
|
}
|
|
if(t.x+1<=200&&!visited[t.x+1][t.y]&&!isprime[map[t.x+1][t.y]])
|
|
{
|
|
tt.x=t.x+1;tt.y=t.y;tt.step=t.step+1;
|
|
Q.push(tt);
|
|
visited[tt.x][tt.y]=true;
|
|
}
|
|
if(t.y-1>=1&&!visited[t.x][t.y-1]&&!isprime[map[t.x][t.y-1]])
|
|
{
|
|
tt.x=t.x;tt.y=t.y-1;tt.step=t.step+1;
|
|
Q.push(tt);
|
|
visited[tt.x][tt.y]=true;
|
|
}
|
|
if(t.y+1<=200&&!visited[t.x][t.y+1]&&!isprime[map[t.x][t.y+1]])
|
|
{
|
|
tt.x=t.x;tt.y=t.y+1;tt.step=t.step+1;
|
|
Q.push(tt);
|
|
visited[tt.x][tt.y]=true;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
int main()
|
|
{
|
|
int u,v,k=1;
|
|
memset(map,0,sizeof(map));
|
|
find_prime();
|
|
build_map(1,1,40000,200);
|
|
while(scanf("%d%d",&u,&v)!=EOF)
|
|
{
|
|
memset(visited,false,sizeof(visited));
|
|
int ans;
|
|
ans=BFS(u,v);
|
|
if(ans) printf("Case %d: %d\n",k++,ans);
|
|
else printf("Case %d: impossible\n",k++);
|
|
}
|
|
return 0;
|
|
}
|