Cannot print out the array of double numbers after mergesort

Question

Please help, keeps getting these errors.

main.cpp: In function ‘int main()’:


main.cpp:177:25: error: cannot convert ‘int*’ to ‘double*’ for argument ‘1’ to ‘void printArray(double*, double)’
 printArray(arr, arr_size);


main.cpp:179:31: error: cannot convert ‘int*’ to ‘double*’ for argument ‘1’ to ‘void mergeSort(double*, int, int)’
 mergeSort(arr, 0, arr_size - 1);
                               ^


main.cpp:183:25: error: cannot convert ‘int*’ to ‘double*’ for argument ‘1’ to ‘void printArray(double*, double)’
 printArray(arr, arr_size);

Code:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

void merge(double arr[], int l, int m, int r)
{
    int i, j, k;
    int n1 = m - l + 1;
    int n2 = r - m;
    int L[n1], R[n2];
    for (i = 0; i < n1; i++)
        L[i] = arr[l + i];
    for (j = 0; j < n2; j++)
        R[j] = arr[m + 1 + j];
    i = 0;
    j = 0;
    k = l;

    while (i < n1 && j < n2)
    {
        if (L[i] <= R[j])
        {
            arr[k] = L[i];
            i++;
        }
        else
        {
            arr[k] = R[j];
            j++;
        }
        k++;
    }

    while (i < n1)
    {
        arr[k] = L[i];
        i++;
        k++;
    }

    while (j < n2)
    {
        arr[k] = R[j];
        j++;
        k++;
    }
}

void mergeSort(double arr[], int l, int r)
{
    if (l < r)
    {
        int m = l + (r - l) / 2;
        mergeSort(arr, l, m);
        mergeSort(arr, m + 1, r);
        merge(arr, l, m, r);
    }
}

void printArray(double A[], int size)
{
    int i;
    for (i = 0; i < size; i++)
        printf("%lf ", A[i]);
    printf("\n");
}

int main()
{
    int arr[1000] = { 0 };
    int arr_size = 0;
    int data;
    char file1[20];
    strcpy(file1, "random.data");
    FILE* fp;
    fp = fopen(file1, "r+");

    if (fp == NULL) // if file not opened return error
    {
        perror("Unable to open file");
        return -1;
    }
    else
    {
        fscanf(fp, "%d", &data);
        arr[arr_size] = data;
        arr_size++;
        while (!feof(fp))
        {
            fscanf(fp, "%d", &data);
            arr[arr_size] = data;
            arr_size++;
        }
    }

    printf("Given array is \n");
    printArray(arr, arr_size);
    mergeSort(arr, 0, arr_size - 1);
    printf("\nSorted array Using MERGE SORT is \n");
    printArray(arr, arr_size);

    return 0;
}

Please format your code before you post here. If your IDE/editor doesn't support code formatting you can use http://format.krzaq.cc/ — Thomas Sablik, Nov 06 '19 at 16:20
Watch out for [Why is “while ( !feof (file) )” always wrong?](https://stackoverflow.com/questions/5431941/why-is-while-feof-file-always-wrong). You've avoided the most common problem, but not some of the subtler things. On third thought, you didn't successfully avoid the common problem. — user4581301, Nov 06 '19 at 16:26
Variable-length arrays like `int L[n1], R[n2];` are not allowed in C++. Also your code looks much more like C so I changed the tag. — Thomas Sablik, Nov 06 '19 at 16:39

score 1 · Answer 1 · answered Nov 06 '19 at 16:26

1

Your array is of type int. Your functions expect a pointer to double. Use either int or double for the array and the functions. Don't mix it. The line

fscanf(fp, "%d", &data);

reads integers so probably you should use the data type int everywhere in your code.

answered Nov 06 '19 at 16:26

Thomas Sablik

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I have changed "%d" to "%lf" but it gives me Given array is 43.720000 60.300000 27.370000 Sorted array Using MERGE SORT is 27.000000 30.000000 it's printing out 0's and not showing numbers after decimals. – maya Nov 06 '19 at 16:31
@maya Then you have to use `double` everywhere in your code. Why do you read a file containing floating point values with `%d` and store the values in an integer array? – Thomas Sablik Nov 06 '19 at 16:34
Okay thanks, sorting works fine. But the extra zeroes after decimal still there. Any advice. – maya Nov 06 '19 at 16:40
@maya you define ```arr``` as an array of ```int``` but then in the functions you say that it should be a ```double[]```. Please be consistent with your types, either use all ```int``` or all ```double``` – John Doe Nov 06 '19 at 16:41
@maya You should read https://en.cppreference.com/w/c/io/fprintf about formatting your output. You can try `printf("%lf.0 ", A[i]);` – Thomas Sablik Nov 06 '19 at 16:45

Cannot print out the array of double numbers after mergesort

1 Answers1