Unknown issue in a sorting algorithm code

Question

I'm a beginnner. This might sound stupid, as its a simple algorithm.The below program compiles successfully but when I run it does not prints the sorted array.The code works fine till the sort algorithm. Then it don't prints the sorted array. what am I doing wrong? Code:

#include <iostream>
#include <cstdlib>

using namespace std;

int main()
{
    int n, i, k = -1;
    cout << "Enter the number of elements: ";
    cin >> n;

    int arr[n];
    cout << "Enter the elements to be sorted: ";
    for (i = 0; i < n; i++)
    {
        cin >> arr[i];
    }
    cout << "The unsorted array: \n";

    for(i = 0; i < n; i++)
    {
        cout << arr[i] << ' ';
    }
    cout << endl;
    //BubbleSort.

    for(int e = n-1; e > 0; --e)
    {
        for (i = 0; i > e; ++i)
        {
            if (arr[i] > arr[i + 1]) {
                arr[i] = k;
                arr[i] = arr[i + 1];
                arr[i + 1] = k;
            }
        }
    }

    cout << "The sorted list: ";

    for (int x = 0; x > n; ++x)
    {
        cout << arr[x] << ' ';
    }

    system("pause");
    return 0;
}

Being a beginner is not an excuse of not debugging your own program — Matt
– Matt, Commented Aug 4, 2014 at 17:30
As @Matt says, you need to learn how to debug your program. Start by printing variables and checkpoints. Then check out a debugging tutorial if you want to go deeper. — keyser
– keyser, Commented Aug 4, 2014 at 17:33
OK, OK!!! For all of those who are having problems to my first sentence.I'm sorry. And I will surely learn to debug the code :p. Any nice tutorials though? :D — Amol Borkar
– Amol Borkar, Commented Aug 4, 2014 at 17:38

P0W · Accepted Answer · 2014-08-04 17:35:48Z

4

"beginners" mistake not really ?

Better use std::cout or a debugger to pin point the mistakes/flaws

Take care of the comparisons, and assignments

arr[i] = k; should be k = arr[i] ;
for (i = 0; i > e; ++i) should be for (i = 0; i < e; ++i)

and

for (int x = 0; x > n; ++x) should be for (int x = 0; x < n; ++x)

edited Aug 4, 2014 at 17:35

answered Aug 4, 2014 at 17:30

P0W

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5 Comments

Amol Borkar Over a year ago

Thanks for the quick reply! But, I modified the code as you suggested, but now its only printing the array as it is, not sorting it. O.O

keyser Over a year ago

You probably shouldn't encourage people to use SO as a debugging tool.

keyser Over a year ago

@EdwardMckinzie Make sure you understand how you should go about finding these errors.

Karoly Horvath Over a year ago

You definitely shouldn't. These kind of questions aren't useful for future visitors.

P0W Over a year ago

@KarolyHorvath @ Keyser Sorry guys, its been a while since I answered a post, I tend forget community rule(s) now and then.

NetVipeC · Accepted Answer · 2014-08-04 17:42:40Z

3

Recommend reread a tutorial about C++ and programming in general, some mistakes are basic ones:

Comparison operators
Assignment

The problematic code:

for (int e = n - 1; e > 0; --e) {
    for (i = 0; i < e; ++i) { // << change here, i > e   ->   i < e you are incrementing
        if (arr[i] > arr[i + 1]) {
            k = arr[i];            // change here, you save in a tmp variable to swap values
            arr[i] = arr[i + 1];
            arr[i + 1] = k;
        }
    }
}

cout << "The sorted list: ";

for (int x = 0; x < n; ++x) { // change here x > n    ->    x < n      same as before.
    cout << arr[x] << ' ';
}

edited Aug 4, 2014 at 17:42

answered Aug 4, 2014 at 17:34

NetVipeC

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