ways to speed up the Full Counting Sort

I encountered a question on hackerrank. https://www.hackerrank.com/challenges/countingsort4

My first attempt passed all the test cases except the last one, due to timeout. After failed to come up with a more efficient algorithm, I improved the code by using StringBuilder instead of concatenating Strings directly. This brought the running time from more than 5 sec to 3.5 sec.

My question is that is there any other way that I can improve the running time? Thanks.

The following is my code.

public class Solution {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int N = scanner.nextInt();
        scanner.nextLine();

        int[] oriNum = new int[N];        
        String[] oriStr = new String[N];
        int[] count = new int[100];
        int[] indices = new int[100];
        int[] output = new int[N];

        // save the originals and the count array
        for (int i = 0; i < N; i++) {
            oriNum[i] = scanner.nextInt();
            oriStr[i] = scanner.nextLine().trim();
            count[oriNum[i]]++;
        }

        // accumulate the count array
        indices[0] = 0;
        for (int i = 1; i < 100; i++) {
            indices[i] = indices[i-1] + count[i-1];
        }

        // output order
        for (int i = 0; i < N; i++) {
            int num = oriNum[i];
            output[indices[num]++] = i;
        }

        int bar = N/2;
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < N; i++) {            
            int index = output[i];
            if (index < bar) 
                sb.append("- ");
            else 
                sb.append(oriStr[index]+ " ");
        }
        System.out.println(sb.toString());
    }
}

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".