Variable Used Before Initialized, But...

[killingthemonkey]

OK, the problem is to write a program to create and populate an array with random numbers. Then, sort the numbers and output the array. The first half is done. I've created an array, and it populate it without issue. (Not without a little help here, by the way.)

The issue comes when I add my sort function. The first use of 'swap' is an assignment. That should initialize it. However, I get a debug error with the following text:
Run-Time Check Failure #3 - The variable 'swap' is being used without being initialized.

The code compiles without an error and the only warning I have is about the implicit conversion of a time_t value to integer. (This is from seeding the random number generator.)

Here is my code.

//randSort.cpp
//Generate 100 random numbers to populate an array
//Sort the numbers
#include <iostream>
#include <stdlib.h>
#include <time.h>
#include <iomanip>
using std::cout;
using std::endl;
using std::setw;

void sort(int array[]);
void output(int array[]);

int main(void)
{
    int large[1000];

    srand(time(NULL));

    for(int i = 0; i < 1000; i++)
    {
        large[i] = 1 + rand() % 1000;
    }

    output(large);
    cout << endl << endl;

    sort(large);

    output(large);
    cout << endl;

    return 0;
}

void sort(int array[])
{
    int i, j, swap;
    int n = sizeof(array);

    for(j = 0; j < 1000; j++)
    {
        for(i = 0; i < 1000; i++)
        {
            if(array[i] > array[i] + 1)
                swap = array[i];
                array[i] = array[i + 1];
                array[i + 1] = swap;
        }
    }

}

void output(int array[])
{
    for(int i = 0; i < 1000; i++)
    {
        if(i % 10 == 0)
            cout << endl;
        cout << setw(4) << array[i] << " | ";
    }
}

[Ikaron]

You need to look over your if statement in the sort function and consider what's going on with it. :)

[killingthemonkey]

Thanks, Ikaron. I had to sit and stare at it, but I finally realized I had forgot my brackets.

Now, can you see what I've done wrong with my bubble sort? It's not sorting.

[Ikaron]

Already saw it. I say unto you once again, consider your if statement. ;)

[killingthemonkey]

Ikaron, thank you again.

Simple placement of the + 1.

[Ikaron]

You're welcome. :)

As a final note, you also have a bug concerning the last iteration of your sort loop (when i == 999) as you may notice after running it.

[killingthemonkey]

Yep. I was getting a Run-Time Check Failure #2 - Stack around the variable 'large' was corrupted.

Fixed it by changing it to i < 999 and j < 999.

The question I have is if the array has 1000 values, wouldn't the largest value be 999?

[Ikaron]

Yes, the last element in a 1000 element array would be 999.

Once again I direct you to consider what happens with the same if statement when i == 999.

[killingthemonkey]

It looks for the value of "i + 1" and dies a horrible death.

Thanks. Now to figure this one out.

[killingthemonkey]

My final code:

//randSort.cpp
//Generate 100 random numbers to populate an array
//Sort the numbers
#include <iostream>
#include <stdlib.h>
#include <time.h>
#include <iomanip>
using std::cout;
using std::endl;
using std::setw;

void sort(int array[]);
void output(int array[]);

int main(void)
{
    int large[1000];

    srand(time(NULL));

    for(int i = 0; i < 1000; i++)
    {
        large[i] = 1 + rand() % 1000;
    }

    output(large);
    cout << endl << endl;

    sort(large);

    output(large);
    cout << endl;

    return 0;
}

void sort(int array[])
{
    int i, j, swap;

    for(j = 0; j < 1000; j++)
    {
        for(i = 0; i < 1000; i++)
        {
            if(i = 999)
            {
                break;
            }
            if(array[i] > array[i + 1])
            {
                swap = array[i];
                array[i] = array[i + 1];
                array[i + 1] = swap;
            }
        }
    }

}

void output(int array[])
{
    for(int i = 0; i < 1000; i++)
    {
        if(i % 10 == 0)
            cout << endl;
        cout << setw(4) << array[i] << " | ";
    }
}

[Ikaron]

Check that new if statement, common error in it. ;)

For someone learning their way around the basics you tackled those problems pretty quick. Keep it up.

[killingthemonkey]

I caught that one quick.

I think it's time to put this one to bed.

Thanks again.