循环语句 + 入门判定

#include <iostream>
#include <iomanip>
using namespace std;
const int N=3005;
int a[N][N];
int n,i,j;
int main() {
  	cin>>n; 
  	int x=0, y=-1,num=1;
  	while(num <= n*n) {
    	while(y+1 < n && a[x][y+1] == 0){
	        ++y;
	    	a[x][y] = num;
			++num;  		
		}
    	while(x+1 < n && a[x+1][y] == 0){
    		++x;
    		a[x][y] = num;
    		++num;
		}     
    	while(y-1 >= 0 && a[x][y-1] == 0){
    		--y;
    		a[x][y] = num;
    		++num;
		}     
    	while(x-1 >= 0 && a[x-1][y] == 0){
    		--x;
    		a[x][y] = num;
    		++num;
		}
  	}
	for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            cout<<a[i][j]<<" ";
        }
        cout<<endl;
    }
  	return 0;
}