Mr. B has recently discovered the grid named "Spiral Grid".
Construct the grid like the following figure. (The grid is actually infinite. The figure was only a small part of it.)
Considering traveling in it, you is free to any cell containing a composite number or 1, but traveling to any cell contai Ning a prime number is disallowed. You can travel up, down, left or right, and not diagonally. Write a program to find the length of the shortest path between pairs of nonprime numbers, or report it ' s impossible.
Inputeach test case was described by a line of input containing the nonprime integer 1 <=x, y<=10,000.
Outputfor Each test case, display its case number followed by the length of the shortest path or "impossible" (without quo TES) in one line.
Sample INPUT1 49 3210 12
Sample outputcase 1:1case 2:7case 3:impossible #include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
using namespace Std;
int book[401][401];
int a[401][401];
int b[401][401];
int vis[160005];
int prime[160005];
struct node
{
int x;
int y;
int s;
} que[160005];
void Make1 ()
{
for (int i=1;i<=160001;i++)
Prime[i]=1;
PRIME[1] = 0;
for (int i = 2; I <= 160001; i++)
{
if (Prime[i])
{
for (int j = 2*i; J <= 160001; j+=i)
PRIME[J] = 0;
}
}
int x, y;
int n=400;
int tot=160000;
a[0][0]=160000;
x=0,y=0;
while (tot>1)
{
while (Y+1<n&&!a[x][y+1])
{
A[x][++y]=--tot;
}
while (X+1<n&&!a[x+1][y])
{
A[++x][y]=--tot;
}
while (Y-1>=0&&!a[x][y-1])
{
A[x][--y]=--tot;
}
while (X-1>=0&&!a[x-1][y])
{
A[--x][y]=--tot;
}
}
for (int i=0; i<400; i++)
for (int j=0; j<400; j + +)
{
if (prime[a[i][j]]==1)
B[i][j]=1;
Else
b[i][j]=0;
}
}
int main ()
{
int t1,t2;
int ans=0;
Make1 ();
while (scanf ("%d%d", &t1,&t2)!=eof)
{
int next[4][2]= {0,1,1,0,0,-1,-1,0};
memset (book,0,sizeof (book));
if (T1==T2)
printf ("Case%d:0\n", ++ans);
Else
{
int Startx,starty,endx,endy;
for (int i=0; i<=399; i++)
for (int j=0; j<=399; j + +)
{
if (A[I][J]==T1)
{
Startx=i;
Starty=j;
}
if (A[I][J]==T2)
{
Endx=i;
Endy=j;
}
}
int head=1,tail=1;
Que[head].x=startx;
Que[head].y=starty;
tail++;
Book[startx][starty]=1;
int flag=0;
while (Head<tail)
{
for (int k=0; k<4; k++)
{
int tx=que[head].x+next[k][0];
int ty=que[head].y+next[k][1];
if (tx<0| | tx>399| | ty<0| | ty>399)
Continue
if (b[tx][ty]==0&&book[tx][ty]==0)
{
Book[tx][ty]=1;
QUE[TAIL].X=TX;
Que[tail].y=ty;
que[tail].s=que[head].s+1;
tail++;
}
if (Tx==endx&&ty==endy)
{
flag=1;
Break
}
}
if (flag==1)
Break
head++;
}
if (flag==1)
printf ("Case%d:%d\n", ++ANS,QUE[TAIL-1].S);
Else
printf ("Case%d:impossible\n", ++ans);
}
}
return 0;
}
hdu4255 Sieve prime number + wide search
