如何在C中找到最接近的平均值元素？

Question

Hi , how can I find the closest number of average in this array? Idk how to do this.

#include<stdio.h>
#include<stdlib.h>
int arraysum();
int main()
{
    int n, A[100], i, b, sum;
    float average;
    printf("Enter number of elements in array: ");
    scanf("%d", &n);
    printf("\nEnter %d numbers: ", n);
    for(i=0; i<n; i++)
        scanf("%d", &A[i]);
    printf("Numbers of this array: ");
    for(i=0; i<n; i++)
        printf("%d ", A[i]);
        
    
    average=arraysum(A, sum, i, n)/n;
    printf("\nAverage is: %.2f", average);       
}
int arraysum(int A[], int sum, int i, int n)
{
    sum=0;
    for(i=0; i<n; i++)
        sum+=A[i];
    return sum; 
}

Thanks in advance, guys! :D

Answer 1

After finding the average, iterate looking for closest.

// Pseudo code
average=arraysum(A, sum, i, n)/n;
best = element 0
for (each element in the array [1...n-1])
  if (|A[i] - average| < |A[best] - average|) 
    best = i

To cope with an average than is not exactly an integer and not use unnecessary floating point math ...

long long scaled_average = arraysum(A, sum, i, n);
best = element 0
for (each element in the array [1...n-1])
  if (|n*A[i] - scaled_average| < |n*A[best] - scaled_average|) 
    best = i

Consider using long long for sum to avoid overflow.

---

Code simplification: no need to pass in sum .

long long arraysum(int A[], int i, int n) {
    long long sum = 0;
    for(i=0; i<n; i++)
        sum+=A[i];
    return sum; 
}

Answer 2

First suggestion is to move the declaration of A[100]; from here

int n, A[100], i, b, sum;   

To just after the scanf() statement, to create a VLA :

    int n, i, b, sum;
    ...
    printf("Enter number of elements in array: ");
    scanf("%d", &n);
    int A[n];
    for(i=0; i<n; i++)
         scanf("%d", &A[i]);

...creating an array just the right size for the need.

Once the array is populated, loop through it and use comparison operators to find the closest to the difference of array values and average . (pseudo code: fabs(a[i]-ave) < fabs(a[i+1]-ave) ) tracking the array index of the array values closest.

Example:

average = arraysum(A, sum, i, n)/(n*(1.0));//divide by floating point

 int closestIndex;
 findClosest(int A, 100, average, &closestIndex);
 printf("Index of value closest to %f is %d\nClosest value is: %d\n",  
            average, closestIndex, A[closestIndex]);

Where findClosest() is defined:

void findClosest(int A[], size_t size, double ave int *index)
{
     int smallestIndex;
     for(int i=0;i<size-1;i++)
     {
          smallestIndex = fabs((double)A[i]-ave) < fabs((double)A[i+1]-ave) ? i : i + 1;
     }
     *index = smallestIndex 
}