Not able to sort an array of int using swapping method in Java

Question

I'm trying to input the length of array and then input the array elements. I was able to check the greatest value in case 1 but I make case 2 to re-sort the array from the smallest number to the biggest, but I wasn't able to do it.

Here's my code:

package peopleinfo;

import java.util.Scanner;

public class mainapp
{
  public static void main(String[] args)
  {
    Scanner sc1 = new Scanner(System.in);
    System.out.println("please input the length of the array:");
    arraybuilder(sc1.nextInt());
  }

  public static void arraybuilder(int i)
  {
    Scanner sc = new Scanner(System.in);
    int[] array = new int[i];
    for (int j = 0; j < array.length; j++)
    {
      int o = j;
      System.out.println("please input the" + ++o + " number");
      array[j] = sc.nextInt();
    }
    for (int j2 = 0; j2 < array.length; j2++)
      System.out.print(array[j2] + "\t");
    System.out.println("what do you want to do ?\n 1 check the biggest number\n2 sort the array from the smallest\nterminate the app");
    int dwc = sc.nextInt();
    switch (dwc)
    {
      case 1:
        int k = 0;
        int max = 0;
        for (int j = 0; j < array.length; j++)
        {
          if (array[j] > k)
          {
            max = j;
            k = array[j];
          }
        }
        System.out.println("the largest number is " + array[max]);
        break;

      case 2:
        int temp;
        boolean fixed = false;
        while (fixed = false)
        {
          fixed = true;
          for (int u = 0; u < array.length - 1; u++)
          {
            if (array[u] > array[u + 1])
            {
              temp = array[u + 1];
              array[u + 1] = array[u];
              array[u] = temp;
              fixed = false;
            }
          }
        }
        for (int j = 0; j < array.length; j++)
        {
          System.out.print(array[j] + "\t");
        }
        break;
      default:
        System.out.println("Error, please rerun the code:)");
        break;
    }
  }
}

I did not understand what am doing wrong?

P.N: should be while(!fixed){ rather than while(fixed=false){ . — Santhosh
– Santhosh, Commented Jul 1, 2015 at 5:30
Making the change in the above comment will not fix the problem as the sorting algorithm being used is incorrect. The while loop serves no purpose and should be removed. — Tim Biegeleisen
– Tim Biegeleisen, Commented Jul 1, 2015 at 5:51

CoderNeji · Accepted Answer · 2015-07-01 05:32:24Z

 case 2:
                int temp;
                boolean fixed = false;
               while (fixed == false) {    // See the change here
                    fixed = true;
                    for (int u = 0; u < array.length - 1; u++) {
                        if (array[u] > array[u + 1]) {
                            temp = array[u + 1];
                            array[u + 1] = array[u];
                            array[u] = temp;
                            fixed = false;
                        }
                    }
                }
                for (int j = 0; j < array.length; j++) {
                    System.out.print(array[j] + "\t");
                }

                break;

In your case 2 the while() loop has fixed = false

Is should be fixed == false i.e. while(fixed==false).

For more info follow the link... Using the assignment operator instead of the equality operator

waterscar · Accepted Answer · 2015-07-01 05:42:18Z

0

while (fixed = false) fixed=false is an assignment, and it will result as a "false" because fixed is assigned as false, which makes the while loop never start.

answered Jul 1, 2015 at 5:42

waterscar

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Comments

KDP · Accepted Answer · 2015-07-01 05:32:56Z

You are assigning the value false to fixed instead of comparing.Change the code as below and check it should work.

 case 2:
            int temp;
            boolean fixed = false;
            while (fixed == false) { //check this line
                fixed = true;
                for (int u = 0; u < array.length - 1; u++) {
                    if (array[u] > array[u + 1]) {
                        temp = array[u + 1];
                        array[u + 1] = array[u];
                        array[u] = temp;
                        fixed = false;
                    }
                }
            }
            for (int j = 0; j < array.length; j++) {
                System.out.print(array[j] + "\t");
            }

            break;

Tim Biegeleisen · Accepted Answer · 2015-07-01 05:46:05Z

0

Your code for the second case is incorrect. You appear to be trying to do a Bubble Sort, but you are missing a second loop. I verified that your current code does not sort the array. Try this code instead:

case 2:
    int temp;
    // Bubble sort the array
    for (int i=0; i < array.length; i++) {
        for (int j=1; j < (array.length - i); j++) {
            if (array[j-1] > array[j]) {
                temp = array[j-1];
                array[j-1] = array[j];
                array[j] = temp;
            }
        }
    }

    for (int j=0; j < array.length; ++j) {
        System.out.print(array[j] + "\t");
    }
    break;

I also removed the while loop logic because it didn't seem to serve any purpose.

edited Jul 1, 2015 at 5:46

answered Jul 1, 2015 at 5:38

Tim Biegeleisen

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1 Comment

CoderNeji Over a year ago

you to made the same mistake... as he had made... just change it... and his code works fine...

Karthik R · Accepted Answer · 2015-07-01 06:38:42Z

0

You have checked for a boolean as while (fixed = false). Please note that you are assigning value there and to check boolean you need to use == like while (fixed == false) or while (!fixed).

Because, when you use while (fixed = false) it doesn't return a boolean value, instead the fixed is assigned as false. You can see that the condition would always be false and the loop wouldn't execute.

edited Jul 1, 2015 at 6:38

answered Jul 1, 2015 at 5:35

Karthik R

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4 Comments

Tim Biegeleisen Over a year ago

Even with this change the sorting code won't produce the desired result.

Karthik R Over a year ago

@TimBiegeleisen Correcting the algorithm as while (fixed == false) works and produces the desired result in sorting the array in ascending order. I have tested it as well. Please let me know if you have any scenario it doesn't work for.

Tim Biegeleisen Over a year ago

So you are basically saying that an array of size N can always be sorted in O(N) time? This doesn't jive with what we know about sorting algorithms.

Karthik R Over a year ago

@TimBiegeleisen I think this question was not about a simple sorting algorithm. It's a single dimensional array in this problem and he tries a simple sorting. The reply was to solve this simple sorting which I think is resolved. The question wasn't even about which algorithm should I be using or shortest path or efficiency, which would have attracted a best approach :) Please add your solution for the efficiency purpose. The usage of fixed == false in while loop haven't been checked by me. I just informed about the code correction to make it work.

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