ACM-蛇形填數

#include<stdio.h>
#include<string.h>
#define MAX 10
int a[MAX][MAX];
void main()
{
	int x,y,tot=1;
	int n;
	scanf("%d",&n);
	x=0;
	y=n-1;
	memset(a,0,sizeof(a));
	a[0][n-1]=1;
	while(tot<n*n)
	{
		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;
		while(y+1<n&&!a[x][y+1])a[x][++y]=++tot;
	}
	for(int i=0;i<n;i++)
	{
		for(int j=0;j<n;j++)
			printf("%4d",a[i][j]);
		printf("\n");
	}
}