Arrays-Wave print Column Wise

#1

why this code is not passing any test case
#include
using namespace std;
int main() {
int m,n,i,j;
cin>>m>>n;
int a[m][n];
for(i=0;i<m;i++)
{
for(j=0;j<n;j++)
{
cin>>a[i][j];
}
}
for(j=0;j<n;j++)
{
if(j%2==0)
{for(i=0;i<m;i++)
{
cout<<a[i][j]<<",";
}
}
else
{
for(i=m-1;i>-1;i–)
{
cout<<a[i][j]<<",";
}
}
}
cout<<“END”;
return 0;
}

#2

for i=-1 i>-1;i-
u have writenb this line wrong