ways to speed up the Full Counting Sort

You should try a plain buffered reader instead of Scanner. Scanner is surprisingly slow and I have participated in programming competitions where Scanner was the sole reason for "time limit exceeded".

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
public class Solution 
{
    public static void main(String[] args)throws Exception 
{
    BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
    int n=Integer.parseInt(in.readLine());
    int[] c=new int[100];
    String[][] dt=new String[100][10300];
    for(int i=0;i<n;i++)
    {
        String[] str=in.readLine().split(" ");
        int val=Integer.parseInt(str[0]);
        if(i<n/2)
            dt[val][c[val]]="-";
        else
             dt[val][c[val]]=str[1];
        c[val]++;
     }
  StringBuilder sb=new StringBuilder("");
    for(int i=0;i<100;i++)
       if(i<n)
        for(int k=0;k<c[i];k++)
            if(dt[i][k]!=null)
               sb.append(dt[i][k]+" ");
            else break;
    System.out.println(sb.toString());
 }
}