Determining the largest non-whole number in C language - c

Question

I'm trying to make a program that accepts 4 numbers, regardless if it is a whole or non-whole number. It will determine the largest non-whole number found in the inputs. If there are no non-whole numbers present, then it will print a message that there are none.
Here is my code:
#include <stdio.h>
int main()
{
float num1, num2, num3, num4;
//Enter Numbers
printf("Enter 4 Numbers : ");
scanf("%f %f %f %f", &num1, &num2, &num3, &num4);
//Numbers are Integer
if ((num1 - (int) num1) == 0
&& (num2 - (int) num2) == 0
&& (num3 - (int) num3) == 0
&& (num4 - (int) num4) == 0) {
printf("Output : No Non-Whole Numbers found\n");
} else {
//Numbers are Float
if (num1 > num2 && num1 > num3 && num1 > num4) {
printf("Output : %.1f\n", num1);
} else if (num2 > num1 && num2 > num3 && num2 > num4) {
printf("Output : %.1f\n", num2);
} else if (num3 > num1 && num3 > num2 && num3 > num4) {
printf("Output : %.1f\n", num3);
} else {
printf("Output : %.1f\n", num4);
}
}
}
But I have some problems with it, for example when a user inputs:
Enter 4 Numbers : 12.5 15 2 1
Output: 15
Instead it should be 12.5
Enter 4 Numbers : 10.5 10.5 7 8
Output: 8.0
Instead it should be 10.5

Answer 1

As Nils Martel pointed out this should be coded as a loop over an array.
The only difference from his implementation is that I think mine is easier to understand, because it's closer to the original code
#include <stdio.h>
#include <stdlib.h>
#define FALSE (0 != 0)
#define TRUE (!FALSE)
#define ABS(x) ((x >= 0) ? (x) : (-x))
#define NUMS 4
int is_whole(float num)
{
return (ABS(num) - (int)ABS(num)) == 0;
}
int main()
{
float nums[NUMS];
int contains_float = FALSE;
int largest = 0; // Initialized with the first element
//Enter Numbers
printf("Enter 4 Numbers : ");
scanf("%f %f %f %f", &nums[0], &nums[1], &nums[2], &nums[3]);
//Numbers are Integer
for (int i = 0; i < NUMS; ++i) {
if (is_whole(nums[i]) == FALSE) {
contains_float = TRUE;
// The additional condition here accounts for the case when
// nums[0] is the largest element in the array
if (nums[i] > nums[largest] || is_whole(nums[largest]))
largest = i;
}
}
if (contains_float)
printf("Output : %.1f\n", nums[largest]);
else
printf("Output : No Non-Whole Numbers found\n");
}
You can run it here https://onlinegdb.com/rkVwPZaZu

Answer 2

I think the best check for determining, if a number is non while would be
floor(n) != n
Now, In your code you repeat yourself quite often and your logic gets quite complex and hard to understand by just looking at it.
You might find this exercise a great moment, to learn more about arrays and loops!
I've tried to rewrite your code using the floor(n) != n check, and by using arrays and loops. Mind, my C is a little rusty, but I hope you can reason with my code:
#include <stdio.h>
#include <math.h>
void print_largest_non_while(float *numbers, int length) {
int is_set = 0;
float greatest;
for (int i = 0; i < length; i++) {
float n = numbers[i];
if (floor(n) != n) {
// n is a non while number
if (!is_set) {
is_set = 1;
greatest = n;
continue;
}
if (greatest < n) greatest = n;
}
}
if (is_set) printf("%f\n", greatest);
}
int main() {
float num[4];
// Enter Numbers
printf("Enter 4 Numbers : ");
scanf("%f %f %f %f", num, num + 1, num + 2, num + 3);
print_largest_non_while(num, 4);
}

Answer 3

Your test consider that all your numbers are not integers, or that they are all integers. Also consider that the test num1 - (int)num1) == 0 could give false results. Better: compare the abs of the difference to a threshold.
#define N 4
#include <stdio.h>
#include <math.h>
int main(){
float num[N];
//Enter Numbers
printf("Enter %d Numbers : ", N);
for (int i = 0; i < N; ++i) {
int t = scanf ("%f", &num[i]);
if (t != 1) return 1;
}
float eps = 1.0e-5;
int found = 0;
float vmax;
for (int i = 0; i < N; ++i) {
int check = fabs(num[i] - rint(num[i])) > eps;
found += check;
if (check) {
if (found == 1) {
vmax = num[i];
} else {
if (num[i] > vmax) {
vmax = num[i];
}
}
}
}
//Numbers are all Integer if found == 0
if(found == 0) {
printf("Output : No Non-Whole Numbers found\n");
} else {
printf("Output : %.1f\n", vmax);
}
return 0;
}