蛇形算法

import java.util.Scanner;

public class Snake{

public static void main(String[] args) {

System.out.println("请输入蛇的维度n：");

Scanner input=new Scanner(System.in);
//班级数n

int a[][] = new int[21][21];
int i,j;
int n=input.nextInt();

for( i=0; i<n; i++)
for (j=0; j<n; j++)
a[i][j] = -1;

int value = 1, max = n*n;
i = 0;
j=n-1;
int inci = 1, incj = 0;
int nexti, nextj;
while(value <= max){
a[i][j] = value ++;
//printf("i=%d, j=%d value=%d\n",i, j, value-1);
nexti = i + inci;
nextj = j + incj;
if( nexti>n-1 || nexti<0 || nextj>n-1 || nextj<0 ||
a[nexti][nextj] != -1)  {
if(inci==1 && incj==0) {
inci= 0; incj=-1;
}
else if(inci==0 && incj==-1) {
inci= -1; incj=0;
}else if(inci==-1 && incj==0) {
inci = 0; incj=1;
}else {
inci = 1;incj=0;
}
nexti = i+inci;
nextj = j+incj;
}
i = nexti;
j = nextj;
}

for (i=0; i<n; i++) {
for(j=0; j<n; j++) System.out.print(a[i][j]+" ");
System.out.println();;
}
}
}