问题

I am new to coding in C and I am trying to get the average of the array but for some reason it is not calculating, it is giving me a result of 0.0.

How can I fix this. Thanks

#include <stdio.h>
float grades_average(float grades[7]);
int main() {

 float grades[7]={98.8, 97.9, 99.3, 99.8, 99.6, 99.4, 99.9};
 float average;
 average = grades_average(grades);
 printf("Average is: %.2f",average);


 return 1;
}
float grades_average(float grades[7]){
 int i;
 float sum = 0;
 float average = 0.0;
 /* calculate the sum of grades using for loop*/
    for(i = 0; i <= 7; i++){
       sum = sum + grades[7];
    }
 average = sum/7;

 return average;
}

The output is:

Average is: 0.00

回答1:

Minimum change solution:

float grades_average(float grades[7]){
 int i;
 float sum = 0;
 float average = 0.0;
 /* calculate the sum of grades using for loop*/
    for(i = 0; i < 7; i++){
       sum = sum + grades[i];
    }
 average = sum/7.f;

 return average;
}

Change for(i = 0; i <= 7; i++){ to for(i = 0; i < 7; i++){. Valid indicies for grades are only 0-6. 7 is out of bounds.
Change sum = sum + grades[7]; to sum = sum + grades[i]; You need to check each element, not the (beyond) last one over and over.
Change average = sum/7; to average = sum/7.f; The .f ensures no integer division. That preserves the decimal during division.

I hope that helps!

回答2:

Here is full code. with 2 changes, Line 20 and Line 23

#include <stdio.h>
float grades_average(float grades[7]);
int main() {

 float grades[7]={98.8, 97.9, 99.3, 99.8, 99.6, 99.4, 99.9};
 float average;
 average = grades_average(grades);
 printf("Average is: %.2f",average);


 return 1;
}
float grades_average(float grades[7]){
 int i;
 float sum = 0;
 float average = 0.0;
 /* calculate the sum of grades using for loop*/

   /*Changed here to <7 because i takes 0,1,2,3,4,5,6 which are 7 elements, your code is <=7 which takes 0.......7 which are 8 elements */
    for(i = 0; i < 7; i++){

       /*Changed here to i from 7, your code everytime sums out of bound element, Garbage value since grades[7] does not exist*/
       sum = sum + grades[i];
    }
 average = sum/7;

 return average;
}

回答3:

Change for(i = 0; i <= 7; i++){} to for(i = 0; i < 7; i++){}, because totally you have 7 elements, starting from 0to6.

Change sum = sum + grades[7]; to sum = sum + grades[i];, as grades[7] will only have the last value of the array, but you want to add all the values present in the array.

include

float grades_average(float grades[7]);
int main() {

 float grades[7]={98.8, 97.9, 99.3, 99.8, 99.6, 99.4, 99.9};
 float average;
 average = grades_average(grades);
 printf("Average is: %.2f",average);


 return 1;
}
float grades_average(float grades[7]){
 int i;
 float sum = 0;
 float average = 0.0;
 /* calculate the sum of grades using for loop*/
    for(i = 0; i < 7; i++){
       sum = sum + grades[i];
    }
 average = sum/7.f;

 return average;
}

Hope that helps..

回答4:

Try by putting i in place of 7,

 sum = sum + grades[7];

sum = sum + grades[i];

and your loop from 0 to 6

回答5:

In place of using this

 sum = sum + grades[7];

Use

sum = sum + grades[i];

Then it will work.

来源：https://stackoverflow.com/questions/45973691/finding-the-average-of-an-array-using-c

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average