蛇形矩阵

#include<stdio.h>
#include<string.h>
const int maxn = 12;//the size of the maze
int a[ maxn ][ maxn ];
const int dx[]={0,1,0,-1};
const int dy[]={1,0,-1,0};
bool inside( int x,int y,int n ){
	if( x>=0&&x<n&&y>=0&&y<n ) return true;
	else return false;
}
int main(){
	int ca;
	scanf("%d",&ca);
	for( int t=0;t<ca;t++ ){
		int n;
		scanf("%d",&n);
		printf("case #%d:\n",t);
		memset( a,0,sizeof( a ) );
		/*
		for( int i=0;i<=n;i++ ){
			a[ i ][ n ] = -1;
			a[ n ][ i ] = -1;
		}
		*/
		int cnt = 1;
		int pos = 0;
		int x,y;
		x = y = 0;
		int tx,ty;
		tx=ty=0;
		while( cnt<=n*n ){
			if( inside( tx,ty,n )==true&&a[ tx ][ ty ]==0 ){
				a[ tx ][ ty ] = cnt++;
				x=tx,y=ty;
			}
			else{
				pos++;
				pos%=4;
			}
			tx=x+dx[pos],ty=y+dy[pos];
			//x += dx[ pos ],y += dy[ pos ];
		}

		for( int i=0;i<n;i++ ){
			for( int j=0;j<n;j++ ){
				if( j==0 ) printf("%d",a[i][j]);
				else printf(" %d",a[i][j]);
			}
			printf("\n");
		}
	}
	return 0;
}