蛇形方阵

例

输入：4

输出：

//
16 15 11 10
14 12  9  4
13  8  5  3
 7  6  2  1

问：如何用下方代码改出来

#include<bits/stdc++.h>
using namespace std;

const int N = 100;
int a[N + 5][N + 5];
int n, x, y, tx, ty, t, num;
int dx[] = {-1, 1};
int dy[] = { 1,-1};

int main(){
	cin >> n;
	x = 1;
	y = 1;
	while(++num <= n * n){
		a[x][y] = num;
		tx = x + dx[t];
		ty = y + dy[t];
		if(tx < 1 || tx > n || ty < 1 || ty > n){
			if(t == 0){
				if(y < n){
					tx = x;
					ty = y + 1;
				}
				else{
					tx = x + 1;
					ty = y;
				}
			}
			if(t == 1){
				if(x < n){
					tx = x + 1;
					ty = y;
				}
				else{
					tx = x;
					ty = y + 1;
				}
			}
			t = ++t % 2;
		}
		x = tx, y = ty;
	}
	for(int i = 1;i <= n;i++){
		for(int j = 1;j <= n;j++){
			cout << setw(3) << a[i][j];
		}
		cout << "\n";
	}
}

玄关，急急急！！！