Find Sum and Average function not returning actual value of Average-CodePudding

Here's my function that returns the Sum of all pair numbers in an array, and the Average of Odd numbers. Although it outputs the Average as zero for some reason.

 #include <stdio.h>
 
 int MoySom(int Tab[],float* Moyenne,int Length)
 {
     int S=0,C=0;
     *Moyenne=0;
     for(int i=0;i<Length;  i)
     {
         if(Tab[i] % 2 == 0)
         {
             S=S Tab[i];
         }
         else if(Tab[i] % 2 != 0)
         {
             *Moyenne =Tab[i];
               C;
         }
     }
     *Moyenne=*Moyenne/C;
     return S;
     
 }
 
 void main()
 {
     int Length,Tab[Length];
     float Moyenne;
     printf("Entrer la longeur de tableau: ");
     scanf("%d",&Length);
     for(int i=0;i<Length;  i)
     {
         printf("Entrer l'element %d: ",i);
         scanf("%d",&Tab[i]);
     }
     printf("Somme est:%d\nMoyenne est: %.2f",
         MoySom(Tab,&Moyenne,Length), Moyenne);
 }

CodePudding user response：

At least these problems:

Wrong declaration order

int Length,Tab[Length]; is junk. The declaration of Tab[Length] is happening, yet the value of Length is indeterminate.

Something more like the below. Declare Tab[] after Length is assigned.

 int Length;
 float Moyenne;
 printf("Entrer la longeur de tableau: ");
 scanf("%d",&Length);
 int Tab[Length];

Better code checks the return value of scanf()

 int cnt = scanf("%d",&Length);
 if (cnt != 1 || Length <= 0) {
   Report_Error_and_exit();
 } 
 int Tab[Length];

Parameter evaluation order assumed

Calculate Moyenne, then used use it.

//printf("Somme est:%d\nMoyenne est: %.2f",
//     MoySom(Tab,&Moyenne,Length), Moyenne);

printf("Somme est:%d\n", MoySom(Tab,&Moyenne,Length));
printf("Moyenne est: %.2f", Moyenne);

Potential /0

*Moyenne=*Moyenne/C; may attempt divide by zero. Better code would prevent that.

Unneeded test

     if(Tab[i] % 2 == 0) {
       S=S Tab[i];
     } else if(Tab[i] % 2 != 0) {
       *Moyenne =Tab[i];

simplifies to

     if(Tab[i] % 2 == 0) {
       S=S Tab[i];
     } else {
       *Moyenne =Tab[i];

CodePudding user response：

There are several issues with your code.

First, you are defining the Tab array in main() using the value of Length, which is not initialized yet. This is not allowed in C, because array sizes must be constant expressions. Instead, you should either use a fixed-size array or dynamically allocate the array using malloc().

Second, you are not checking whether C is zero before dividing *Moyenne by C to calculate the average. If C is zero, then this will result in a division by zero, which is undefined behavior. You should check for this condition and handle it properly.

Here is how you can fix these issues and properly calculate the sum of even numbers and the average of odd numbers in the array:

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

int MoySom(int* Tab, float* Moyenne, int Length)
{
  int S = 0, C = 0;
  *Moyenne = 0;
  for (int i = 0; i < Length;   i)
  {
    if (Tab[i] % 2 == 0)
    {
      S = S   Tab[i];
    }
    else if (Tab[i] % 2 != 0)
    {
      *Moyenne  = Tab[i];
        C;
    }
  }
  if (C > 0)
  {
    *Moyenne = *Moyenne / C;
  }
  return S;
}

void main()
{
  int Length;
  float Moyenne;
  printf("Entrer la longeur de tableau: ");
  scanf("%d", &Length);

  // Dynamically allocate the array using malloc()
  int* Tab = malloc(Length * sizeof(int));
  if (Tab == NULL)
  {
    // Handle allocation failure
    printf("Erreur d'allocation de memoire!\n");
    return;
  }

  for (int i = 0; i < Length;   i)
  {
    printf("Entrer l'element %d: ", i);
    scanf("%d", &Tab[i]);