Why am I getting a run time error in Google code jam?

Vestigium means "trace" in Latin. In this problem, we work with Latin squares and matrix traces.
The trace of a square matrix is the sum of the values on the main diagonal (which runs from the upper left to the lower right).
An N-by-N square matrix is a Latin square if each cell contains one of N different values, and no value is repeated within a row or a column. In this problem, we will deal only with "natural Latin squares" in which the N values are the integers between 1 and N.
Given a matrix that contains only integers between 1 and N, we want to compute its trace and check whether it is a natural Latin square. To give some additional information, instead of simply telling us whether the matrix is a natural Latin square or not, please compute the number of rows and the number of columns that contain repeated values.

It runs in Intellij

class Main 
{
public static void main(String args[])
{
Scanner sc = new Scanner(System.in);
int T=sc.nextInt();
for(int z=1;z<=T;z++)
{
int size=sc.nextInt();
int mat[][]=new int[size][size];
for(int i=0;i<size;i++)
{
for(int j=0;j<size;j++)
{
mat[i][j]=sc.nextInt();
}
}
int k=trace(mat,size);
int r=row_duplicate(mat,size);
int c=col_duplicate(mat,size);
System.out.println("Case #" +z+ ":"+" " +k+ " " +r+ " " +c); //Case #1: 4 0 0
}
}
public static int trace(int arr[][],int size)
{
int sum=0;
for(int i=0;i<size;i++)
{
for(int j=0;j<size;j++)
{
if(i==j)
sum=sum+arr[i][j];
}
}
return sum;
}
public static int row_duplicate(int arr[][],int size)
{
Hashtable<Integer,Integer> h=new Hashtable<>();
int count=0;
for(int i=0;i<size;i++)
{
int row[]=arr[i];
for(int j=0;j<row.length;j++)
{
if(h.containsKey(row[j]))
{
count++;
break;
}
else
{
h.put(row[j],1);
}
}
h.clear();
}
return count;
}
public static int col_duplicate(int arr[][],int size)
{
Hashtable<Integer,Integer> h=new Hashtable<>();
int count=0;
for(int i=0;i<size;i++)
{
for(int j=0;j<size;j++)
{
int ele=arr[j][i];
if(h.containsKey(ele))
{
count++;
break;
}
else
{
h.put(ele,1);
}
}
h.clear();
}
return count;
}
}

I think you should mention your class name 'Solution'.
for further information go through the link

The problem is that you are not importing Scanner class properly.
Add this line at the top: import java.util.*;

Change the class name to Solution instead of Main

i.e

import java.util.*;
import java.io.*;
class Solution{
public static void main(String[] args){
// TODO Auto-generated method stub
Scanner sc = new Scanner(System.in);
int t = sc.nextInt();
int k =1;
while(t > 0)
{
int n = sc.nextInt();
int m[][] = new int[n][n];
int rows = 0, columns = 0;	
for(int i = 0 ; i < n ; i++)
{
for(int j = 0 ; j < n ;j++)
{
m[i][j] = sc.nextInt();
}
}
int sum = 0;
for(int i = 0 ; i < n ; i++)
{
sum+= m[i][i];
}
for(int i = 0 ; i < n ; i++)
{
HashSet<Integer> h = new HashSet<>();
for(int j = 0 ; j < n ; j++)
{
h.add(m[i][j]);
}
if(h.size() < n)
{
rows++;
}
}
for(int i = 0 ; i < n ; i++)
{
HashSet<Integer> h = new HashSet<>();
for(int j = 0 ; j < n ; j++)
{
h.add(m[j][i]);
}
if(h.size() < n)
{
columns++;
}
}
System.out.printf("Case #%d: %d %d %d\n", k, sum, rows, columns);
k++;
t--;
}
}
}

here is the python implementation of the code, this is working for all the test cases
feel free to ask if you encounter an issue

T = int(input())
for i in range(1,T+1):
size=int(input())
column =[]
r = 0
c = 0
k = 0
for a in range(size):
row = list(map(int,input().split()))
column.append(row)
for q in range(size):
k=k+column[q][q]
for q in column:
for z in q:
if q.count(z)>1:
r = r+1
break
column = [[column[j][i] for j in range(len(column))] for i in range(len(column[0]))]
for q in column:
for z in q:
if q.count(z)>1:
c = c+1
break
i=str(i)
print("Case #"+i+":",k,r,c)