https://www.acwing.com/problem/content/3211/

#include<bits/stdc++.h>
using namespace std;
const int N=510;
int dx[]={0,1,1,-1},dy[]={1,-1,0,1};
int n;
int a[N][N];
int main()
{
    cin>>n;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            scanf("%d",&a[i][j]);
        }
    }
    int count=0;
    bool st=false;
    int i=0;
    int x=1,y=1;
    int len=n*n-1;
    int flag=1;
    printf("%d ",a[1][1]);
    while(len--){
        i=i%4;

        x=x+dx[i],y=y+dy[i];
        if(x<=0||y<=0||x>n||y>n){
            x=x+dx[(i+1)%4],y=y+dy[(i+1)%4];
        }
        printf("%d ",a[x][y]);
        if(i==1||i==3){
            if(flag!=count){
            flag++;
            continue;
            }

        }

        if(count==n-1)st=true;
        if(i==0||i==2){
            flag=1;
            if(st==false)count++;
            else count--;
        }
        i++;
    }
    return 0;
}