[Solved] The result of my code is zero and I don’t know why

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I found 2 mistakes – Your answer is coming to be 0 always because in the array [4,7,8,9] 9 is the largest biggest non prime number and there is no prime number greater than 9 in your array.
if the input array is [4,7,8,9,11] the output is 11 as 11 is smallest prime number greater than 9.

Second mistake instead of using this

if(CheckPrimeNum(a[i])==2 && a[i]> BiggestNotPrime(a,n))
            SmallestPrimeLocation =i;
            break;

You should be using 

 if(CheckPrimeNum(a[i])==2 && a[i]> BiggestNotPrime(a,n))
 {       SmallestPrimeLocation =i;
         break;
 }

This is because your break statement was oustide if condition and loop was getting executed just once.

However you have complicated a simple task, a simpler code can be something like this
Working code-

#include <bits/stdc++.h>
using namespace std;

void TypeIn(int a[] ,int &n)
    {
            cout<< "\nType in n: ";
            cin >> n;
            for(int i=0; i<n; i++)
                {
                cout << "a[" << i << "]= ";
                cin >> a[i];
                }
    }
bool isPrime(int n) 
{ 
    // Corner case 
    if (n <= 1)  return false; 

    // Check from 2 to n-1 
    for (int i=2; i<n; i++) 
        if (n%i == 0) 
            return false; 

    return true; 
} 
int BiggestNotPrime(int a[], int n)
{
    int BiggestNotPrimeNum =0;
    for( int i=0; i<n; i++)
    {
        if(!isPrime(a[i]))
        {
             BiggestNotPrimeNum = a[i];
        }
    }

    return BiggestNotPrimeNum;
}

int main()
{

    int n;
    int a[100];
    TypeIn(a,n);
    //sorting the array is important
    sort(a,a+n);
    int SmallestPrimeLocation =-1;
    int BiggestNotPrimeNum =  BiggestNotPrime(a,n);
    for(int i=0; i<n; i++)
        {
        if(a[i]> BiggestNotPrimeNum && isPrime(a[i]))
        {
             SmallestPrimeLocation =i;
            break;
        }

    }
    if(SmallestPrimeLocation ==-1)
    {
        cout << "No number found"<<endl;
    }
    else
    {
        cout<<a[SmallestPrimeLocation]<<endl;
    }

}

solved The result of my code is zero and I don’t know why