蛇形问题

#include <stdio.h>
#include<string.h>
#define maxn 20
int a[maxn][maxn];
int main(int argc, char *argv[])
{   int n,tt=0,x,y;
scanf("%d",&n);
memset(a,0,sizeof(a));
tt=a[x=0][y=n-1]=1;


while(tt<n*n)
{
while(x+1<n&&a[x+1][y]==0)a[++x][y]=++tt;
while(y-1>=0&&a[x][y-1]==0)a[x][++y]=++tt;
while(x-1>=0&&a[x-1][y]==0)a[--x][y]=++tt;
while(y+1<n&&a[x][y+1]==0)a[x][++y]=++tt;
}
for(x=0;x<n;x++)
{for(y=0;y<n;y++)
printf("%3d ",a[x][y]);
printf("\n");}
return 0;
}