Question

Complete the function main in file median.c to implement the computation of the median of a sequence of integers read from stdin. The program should use realloc to allow an arbitrary number of integers to be read into a dynamically allocated array. Every time realloc is called, let the new size of the array be twice the old size plus 1. Look at function readLongLine in the slides for Chapter 6 for an example of how to use realloc. The program should return -1 if anything other than an integer is read from stdin. A test script is provided in test_median.sh.

Note that median.c uses qsort from the standard library to sort the array of integers. We have not seen how to call qsort yet, so don't worry if it still looks mysterious. It involves passing a function pointer, which we shall cover shortly.

Here is the function

#include <stdio.h>
#include <stdlib.h> /* for realloc, free, and qsort */

/*
* Read integers from stdin until EOF. Then
* print the median of the numbers read.
*/

/*
* Print the median of a sequence of sorted integers.
*/
void printMedian(int const * numbers, int cnt) {
int i, halfWay;
double median;
/* debugging printout of sorted array */
for (i = 0; i < cnt; i++) {
    printf("%d%c", numbers[i], i == cnt-1 ? '\n' : ' ');
}
halfWay = cnt / 2;
if (halfWay * 2 == cnt) {
    /* cnt is even: average two middle numbers */
    median = 0.5 * (numbers[halfWay] + numbers[halfWay-1]);
} else {
    /* cnt is odd: take middle number */
    median = numbers[halfWay];
}
printf("Median of %d integers: %g\n", cnt, median);
}

/* Integer comparison function for qsort. */
static int icompare(void const * x, void const * y) {
int ix = * (int const *) x;
int iy = * (int const *) y;
return ix - iy;
}

int main(void) {
/* Size of allocated array. */
size_t size = 0;
/* Number of ints stored in the array. Must be less
   * than or equal to size at all times. */
size_t cnt = 0;
/* Pointer to dynamically allocated array. */
int * numbers = 0;
/* Variables used by scanf. */
int num, ret;
while ((ret = scanf("%d", &num)) != EOF) {
    /* Your code here. */
}
if (!numbers) {
    printf("Read no integers. Median undefined.\n");
    return -1;
}
/* Sort numbers in ascending order. */
qsort(numbers, cnt, sizeof(int), icompare);
printMedian(numbers, cnt);
free(numbers);
return 0;
}

How do I go about finishing this? This is in C language remember that.

Answer 1