Determine maximum value of array using a function in c [closed] - c

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Write a program takes n number of element from user (where, n is specified by user) and stores data in an array.
Then, display the contents of the array on the screen and calculate and display the largest of the temperatures using function.
I understand the question but every time I tried, I always get errors. Can someone correct my code:
#include <stdio.h>
float maximum (float num[]);
int main ()
{
int i,size;
printf ("Enter total number of elements (1 to 100): \n");
scanf ("%d", &size);
float num[]={size};
for (i=1; i<=size; i++) {
printf ("Enter Number %d: ",i);
scanf ("%f", &num[i]); }
printf("Largest Number: %f", maximum (float num[]);
}
float maximum (float num[])
{
int i,size;
float num[]={size};
float max;
max=num[1];
for (i=2; i<=size; i++) {
if (num[i]>max)
max=num[i]; }
return max;
}
thanks

Answer 1

you need something like this.
#include <stdio.h>
float maximum (float num[], int size);
int main ()
{
int i,size;
printf ("Enter total number of elements (1 to 100): \n");
scanf ("%d", &size);
float num[100];
for (i=0; i<size; i++) {
printf ("Enter Number %d: ",i);
scanf ("%f", &num[i]); }
printf("Largest Number: %f", maximum (num, size);
}
float maximum (float num[], int size)
{
int i;
//float num[]={size};
float max;
max=num[0];
for (i=1; i<size; i++) {
if (num[i] > max)
max=num[i]; }
return max;
}

Answer 2

float num[size]={0};
VLA with size number of elements.
Also scanf ("%f", &num[i-1]); otherwise you were accessing array index out of bound invoking UB.
Also in the function
float maximum (float num[])
{
int i,size;
//float num[]={size};
float max;
max=num[0];
for (i=2; i<=size; i++) {
if (num[i-1]>max)
max=num[i-1];
}
return max;
}
Example code:
#include <stdio.h>
#include <stdlib.h>
float mymaximum (int size, float num[]);
int main (void)
{
int i,size;
printf ("Enter total number of elements (1 to 100): \n");
if( scanf ("%d", &size) != 1){
fprintf(stderr,"Error in input");
exit(1);
}
if( size<1 && size>100){
fprintf(stderr,"Wrong input.");
exit(1);
}
float num[size];
for (i=0; i<size; i++) {
printf ("Enter Number %d: ",i);
if( scanf ("%f", &num[i]) !=1){
fprintf(stderr,"Error in input");
exit(1);
}
}
printf("Largest Number: %f", mymaximum(size,num));
return 0;
}
float mymaximum (int size, float num[])
{
float max=num[0];
for (int i=1; i<size; i++) {
if (num[i]>max)
max=num[i];
}
return max;
}
So what were the problems?
float num[]={size}; This is one element array. And then you try to access all the other indices other than 0. This will be accessing an memory out of the array's bound. You have 1 elelemnt array and unless size = 1 that's Undefined behvaior. Anything can happen. Anything including blowing up the code or sudden working at a time.
What was the solution?
Incorporated some error check. In case the user gives wrong input or the number of elements is more than what you expect it to be, then we are terminating the program. Instead of using 100 element array we have used VLA and created an array having size number of elements.
What happened in mymaximum function?
Earlier you have redeclared an one element array in the method. That's wrong - You passed the array so that you can read it. But you didn't do it. Rather you declared again an array and accessed the positions out of the array bounds. Yes again it is undefined behavior.