CODEWITHSUNDEEP
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eyu
eyu

Reputation: 1

Java stdin not prompting program to run

I am working on a Merge-sort algorithm, and I am currently trying to test if it works.

It should be controlled through stdin with the input format:

array length element values (separated by " ")

However, when typing in:

3
17 10 3

Nothing happens, and hitting enter, just get me to the next line in the console.

I get no error message (unless I type in wrong input), and so I have a hard time figuring out why the script is not prompted to run with the input given.

(Code is copied below)

package merge;

import java.io.*;
import java.util.*;

public class MergeSort
{
    // This method takes two sorted arrays of integers as input parameters
    // and it should return one sorted array of integers.
    public int[] merge(int[] A1, int[] A2) {
        int[] C = new int[A1.length + A2.length];
        int i = 0, j = 0, k = 0;
        while (i < A1.length && j < A2.length)
            C[k++] = A1[i] < A2[j] ? A1[i++] :  A2[j++];

        while (i < A1.length)  
            C[k++] = A1[i++];

        while (j < A2.length)    
            C[k++] = A2[j++];

        return C;
    }

    // This method takes an array of integers as input parameter,
    // and it should then return the integers sorted
    // in ascending order using the MergeSort algorithm.
    private int[] sort(int[] numbers) {
        //pointers
        int i = 0, j = 0, k = 0;
        // reference values
        int half = numbers.length / 2;
        int[] sorted = new int[numbers.length];

        if (numbers.length <= 1){
            return numbers;
        }

        //left part of 'numbers'
        int[] left = new int[half];
        int[] right;

        //right part of 'numbers' 
        if (numbers.length % 2 != 0){
            right = new int[half+1];
            j = half + 1;
        }
        else{
            right = new int[half];
            j = half;
        }
        //fills out left half of array with values from input array
        while (i < half)
            left[i] = numbers[i];
            i++;

        //fills out right half of array with values from input array
        while (j < numbers.length)
            right[j] = numbers[k];
            j++; k++;

        left = sort(left);
        right = sort(right);

        merge(left,right);

        return sorted;
    }

    // ##################################################
    // # Stdin part. #
    // ##################################################

    public static void main(String[] args) throws IOException {
        new MergeSort().run();
    }

    private void run() throws IOException {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        int[] numbers = readIntArray(in);

        numbers = sort(numbers);
        for (int i = 0; i < numbers.length; i++) {
            System.out.print(numbers[i] + " ");
        }
    }

    private int[] readIntArray(BufferedReader in) throws IOException {
        int length = Integer.parseInt(in.readLine());
        int[] array = new int[length];
        StringTokenizer st = new StringTokenizer(in.readLine());

        for (int i = 0; i < length; i++) {
            array[i] = Integer.parseInt(st.nextToken());
        }
        return array;
    }
}

Upvotes: 0

Views: 81

Answers (1)

Emmanuel Lonca
Emmanuel Lonca

Reputation: 196

You call readLine() two times, resulting in an attempt to read two lines on the standard input.

Upvotes: 1

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