Zig-Zag Traversal

//this code shows how to interchange diagonals when i%2==0 and printing a[i][j] and if not a[i][m-j-1]
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int n;
    int m;
    cin>>n>>m;
    int a[n][m];
    for(int i=0;i<n;i++)
    {
        for(int j=0;j<m;j++)
        {
            cin>>a[i][j];
        }
    }
    for(int i=0;i<n;i++)
    {
        for(int j=0;j<m;j++)
        {
           if(i%2==0)
           {
               cout<<a[i][j]<<" ";
           }
            else
            {
                cout<<a[i][m-j-1]<<" ";
            }
        }
    }
    
    return 0;
}