Getting Error While Calculating Average in Array More Than 4 Elements in C

The defects in the code:

1. Used the variable input uninitialized to initialize an array.

2. Attempted to get the size of the array which has incorrectly determined previously.

3. The variable size is never used in the entire program (redundant declaration).

Note: I'll be using -std=c99 (C99 standard)

gcc -std=c99 -o main main.c; ./main

Code redefined (read the added comment to get the issue solved):

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

int main(void) {
    srand(time(NULL));

    int sum, i, input;
    float average;
    sum = average = 0;

    printf("Type the value of your array : ");
    scanf("%d", &input);

    int array[input]; // placing after defining of 'input'
    // int size = sizeof(array) / sizeof(array[0]); // unused variable

    printf("The size of your array is : %.2d \n", input);

    for (i = 0; i < input; i++)
        array[i] = rand() % 100 + 1;

    // loop for printing results

    for (i = 0; i < input; i++) {
        printf("Element %d; %d \n", i, array[i]);
        sum += array[i];
    }

    average = (float) sum / i;

    printf("The average of array values is %.2f \n", average);

    return 0;
};

This will output:

Type the value of your array : 10 
The size of your array is : 10 
Element 0; 6
Element 1; 14
Element 2; 66
Element 3; 73
Element 4; 19
Element 5; 14
Element 6; 62
Element 7; 78
Element 8; 31
Element 9; 31
The average of array values is 39.40