Array Problem - 01

Problem:

Given an unsorted array of size n containing the integers 1 through n in random order with one element randomly replaced by 0, determine the missing element most efficiently.

Here was the solution I came up with:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
     
void InitArray (int *TheArray, int n)
{
     // Fill the array with values 1..n
     for (int i = 0; i < n; i++)
         TheArray[i] = i+1;
                   
     // Remove a value at random.
          TheArray[rand() % n] = 0;      
}
     
// From: http://codesam.blogspot.com/2011/04/how-to-shuffle-array-or-fisher-yates.html
// With reasoning from CodingHorror: http://www.codinghorror.com/blog/2007/12/the-dangerof-naivete.html
// Original Theory: http://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
void KnuthShuffle(int *orgArray, int arraySize)
{
     if (arraySize == 0 || arraySize == 1)
          return;
     
     int i;
     int index, temp;
     for (i = arraySize - 1; i > 0; i--)
     {
          index = rand() % (i+1);
          temp = orgArray[index];
          orgArray[index] = orgArray[i];
          orgArray[i] = temp;
     }
}
     
void PrintArray (int *TheArray, int n)
{
     printf ("TheArray[%d]: {%d", n, TheArray[0]);
           
     for (int i = 1; i < n; i++)
          printf (", %d", TheArray[i]);
           
     printf ("}\n");
}
     
int main(int argc, char *argv[])
{
     // Sum of integers between 1 and n = n(n+1)/2
          
     int n = 9;         
     int TheArray[n];   
     int TotalValue = 0;
           
     // Check for arguement passed to the program to define n.
     if (argc == 2)
          n = atoi(argv[1]);
                   
     // Seed the randomizer with the current time.
     srand(time(NULL));
                   
     InitArray (TheArray, n);
     KnuthShuffle (TheArray, n);
     PrintArray (TheArray, n);
                   
     // And we will avoid a function here..
     for (int x = 0; x < n; x++)
          TotalValue += TheArray[x];
                   
     printf ("The missing number is: %d!\n", ((n*(n+1))/2) - TotalValue);
           
     return 0;
}

 This code accepts input from the command line to specify n. If I see a way to optimize it more I will do so at a later time.

EDIT:
Ack, I just realized that I defined TheArray with the default value BEFORE checking the command line arguments. It wasn't too long before I was grabbing data from outside the array's boundaries. This is what I get for adding the command line functionality at the last second.

A simple fix would be to replace the beginning of the main function with:

#include <stdio.h>
int main(int argc, char *argv[])
{
     // Sum of integers between 1 and n = n(n+1)/2
          
     // Check for arguement passed to the program to define n.
     int n;

     if (argc == 2)
          n = atoi(argv[1]);
     else
          n = 9;
        
     int TheArray[n];   
     int TotalValue = 0;
 . . .

That works much better.