Question

I’ve tried for a couple hours to get this working, but for whatever reason I can’t get my array to print correctly. Here is my code (.txt file below)

//
//  main.cpp
//  cs498 -mp1

#include<iostream>
#include<stdlib.h>
#include <fstream>
#include<time.h>

int sortsize=1000;
int seed=1;

using namespace std;

void readfile(int *input, int size)

{

}

void writefile(int *input, int size)
{
    ofstream myfile;
    myfile.open ("example.txt");
    myfile << "Radix Sort\n";

    for(int i=0; i<size; i++)
        myfile << input[i] << endl;
    myfile.close();

}


void radixsort(int *a, int arraySize)
{
    int i, bucket[sortsize], maxVal = 0, digitPosition =1 ;
    for(i = 0; i < arraySize; i++) {
        if(a[i] > maxVal) maxVal = a[i];
    }

    int pass = 1; 
    while(maxVal/digitPosition > 0) {
        // reset counter 
        int digitCount[10] = {0};

        // count pos-th digits (keys) 
        for(i = 0; i < arraySize; i++)
            digitCount[a[i]/digitPosition%10]++;

        // accumulated count 
        for(i = 1; i < 10; i++)
            digitCount[i] += digitCount[i-1];

        // To keep the order, start from back side
        for(i = arraySize - 1; i >= 0; i--)
            bucket[--digitCount[a[i]/digitPosition%10]] = a[i];

        for(i = 0; i < arraySize; i++)
            a[i] = bucket[i];

        cout << "pass #" << pass++ << ": ";
        digitPosition *= 10;
    } 

}

void ccradixsort(int *array /* you will need more arguments */)
{

}

int main(int argc, char *argv[])
{
    clock_t start, end;
    int *sortarray;
    int *input;

    if(argc > 1)
        sortsize = atoi(argv[1]);

    sortarray = (int *) malloc(sortsize * sizeof(int));
    input = (int *) malloc(sortsize * sizeof(int));

    if(/*argc == 3*/ true)
    {
        seed = atoi(argv[2]);
        for(int i = 0; i < sortsize; i++)
        {
            input[i] = rand();      
        }
    }
    else
    {
        readfile(input,sortsize);
    }

    for(int i = 0; i < sortsize; i++)
    {
        sortarray[i] = input[i];
    }

    start = clock();
    radixsort(sortarray, sizeof(sortarray));
    end = clock();

    cout << "Sorted in " << (double)(end - start)/CLOCKS_PER_SEC << " seconds by radixsort()" << endl;
    writefile(sortarray, sortsize);

/*  
    for(int i = 0; i < sortsize; i++)
    {
        sortarray[i] = input[i];
    }

    start = clock();
    ccradixsort(sortarray);
    end = clock();

    cout << "Sorted in " << (double)(end - start)/CLOCKS_PER_SEC << " seconds by ccradixsort()" << endl;

    //if(argc != 3)
    //  writefile(sortarray, sortsize);
*/
}

And here’s a portion of the text file it generates:

>Radix Sort

>16807  
>101027544  
>282475249  
>470211272  
>984943658  
>1144108930  
>1457850878  
>1622650073  
>1458777923  
>2007237709  
>823564440  
>1115438165 

Answer 1

Here:

radixsort(sortarray, sizeof(sortarray));

Because sortarray is an int*, sizeof(sortarray) is only 4 or 8 (depending on your target).

You should probably use sortsize like you do elsewhere.