Write a program that uses a function to find the highest number in an array containing 5 numbers

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Question

Write a program that uses a function to find the highest number in an array containing 5 numbers.

In the main(), you must ask the user to enter 5 numbers and store these in the array.

Pass the array to a function and your function must find the highest number.

Return this number to your main() and display it.

Further

This is all I have written so far. Stuck on the operation to determine the highest number within the function. Any help would be appreciated.

#include <stdio.h>
#include <math.h>

#define SIZE 5

//function signatures
int getHighestNumber(int[]);

//main function
int main() 
{
    //main variables
    int array[SIZE];
    int highest_number;
    int i;

    printf("\nPlease enter 5 numbers into an array.\n");

    for (i = 0; i < SIZE; i++)
    {
        scanf("%d", &array[i]);
    }

    int getHighestNumber(int array[SIZE]);

    return 0;
}

int getHighestNumber(int array[]) 
{
    //function variables
    int highest_number;
    int i;

    for (i = 0; i < SIZE; i++) 
    {
        if (array[i] > highest_number)
        {
            highest_number = array[i]; 
        }
    }
    
    return highest_number;
}
function-definition function-call max c arrays
2 Answers

For starters this line

int getHighestNumber(int array[SIZE]);

is not a function call. It is a function declaration.

You need to write

highest_number = getHighestNumber( array );

The function itself should be declared at least like

int getHighestNumber( const int[]);

Within the function the variable highest_number was not initialized. So the function invokes undefined behavior. The function can be defined the following way

int getHighestNumber( const int array[]) 
{
    //function variables
    int highest_number = array[0];
    for ( int i = 1; i < SIZE; i++) 
    {
        if (array[i] > highest_number)
        {
            highest_number = array[i]; 
        }
    }
    
    return highest_number;
}

Or for a documentation purpose you could declare the function parameter like

int getHighestNumber( const int array[SIZE])
{
    //...
}
user_28772410

Another way to get max without loop using recursion :

#include <stdio.h>
#define SIZE 5

//function signatures
int getHighestNumber(int[],int);

//main function
int main() 
{
    // main variables
    int array[SIZE];
    int highest_number;
    int i;

    printf("\nPlease enter 5 numbers into an array.\n");

     for (i = 0; i < SIZE; i++)
    {
        scanf("%d", &array[i]);
    }

    int max = getHighestNumber(array,SIZE);
    printf("%d\n",max);

    return 0;
}

int getHighestNumber(int array[], int size) 
{
    // if size of array is 1 the max is the only 
    // of the array 
    if (size == 1) return array[0];
    
    // else max is the max between first element and the next element
    int max = getHighestNumber(&array[1],size-1);
    if (max > array[0])
        return max;
    return array[0];
}
user_139447500
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