the results:

The max value in the array is: 7

The codes:

//obtain the max value from an array by recrusive method
#include <iostream>
#include <iomanip>
using namespace std;
int getMaxValue(int array[], int n);
int main()
{
    int a[] = {1,2,3,4,5,6,7};
    cout << "The max value in the array is: " << getMaxValue(a, 7) << endl;
    return 0;
}
int getMaxValue(int array[], int n)
{
    if (n == 0){
        return array[0]; 
    }
    return max(array[n-1], getMaxValue(array, n-1));
}

PS C:\Users\Desktop\C++\FirstProgram> .\practice.exe
6
The max value in the array is: 20
The elements in array
 14 20 13  2  5 13

The corresponding codes:

//obtain the max value from an array by recrusive method
#include <iostream>
#include <iomanip>
#include <ctime>
#include <cstdlib>
using namespace std;
int getMaxValue(int array[], int n);
void generate_array(int* &array, int n); //The reference function could help transfer argument 
void display_array(int array[], int n); 
int main()
{
    srand((unsigned)time(NULL));
    int n;
    cin >> n;
    int* a;
    generate_array(a, n);
    cout << "The max value in the array is: " << getMaxValue(a, n) << endl;
    display_array(a, n);
    free(a);
    return 0;
}
int getMaxValue(int array[], int n)
{
    if (n == 0){
        return array[0]; 
    }
    return max(array[n-1], getMaxValue(array, n-1));
}
void generate_array(int* &array, int n)
{
    array = new int[n];
    for(int i = 0; i < n; i++){
        array[i] = rand() % 20 +1;
    }
}
void display_array(int array[], int n)
{
    cout << "The elements in array" << endl;
    for(int i = 0; i < n; i++){
        cout << setw(3) << array[i];
    }
}