ternary search c++

// C++ program to illustrate 
// recursive approach to ternary search 
#include <bits/stdc++.h> 
using namespace std; 
  
// Function to perform Ternary Search 
int ternarySearch(int l, int r, int key, int ar[]) 
{ 
    if (r >= l) { 
  
        // Find the mid1 and mid2 
        int mid1 = l + (r - l) / 3; 
        int mid2 = r - (r - l) / 3; 
  
        // Check if key is present at any mid 
        if (ar[mid1] == key) { 
            return mid1; 
        } 
        if (ar[mid2] == key) { 
            return mid2; 
        } 
  
        // Since key is not present at mid, 
        // check in which region it is present 
        // then repeat the Search operation 
        // in that region 
        if (key < ar[mid1]) { 
  
            // The key lies in between l and mid1 
            return ternarySearch(l, mid1 - 1, key, ar); 
        } 
        else if (key > ar[mid2]) { 
  
            // The key lies in between mid2 and r 
            return ternarySearch(mid2 + 1, r, key, ar); 
        } 
        else { 
  
            // The key lies in between mid1 and mid2 
            return ternarySearch(mid1 + 1, mid2 - 1, key, ar); 
        } 
    } 
  
    // Key not found 
    return -1; 
} 
  
// Driver code 
int main() 
{ 
    int l, r, p, key; 
  
    // Get the array 
    // Sort the array if not sorted 
    int ar[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; 
  
    // Starting index 
    l = 0; 
  
    // length of array 
    r = 9; 
  
    // Checking for 5 
  
    // Key to be searched in the array 
    key = 5; 
  
    // Search the key using ternarySearch 
    p = ternarySearch(l, r, key, ar); 
  
    // Print the result 
    cout << "Index of " << key 
         << " is " << p << endl; 
  
    // Checking for 50 
  
    // Key to be searched in the array 
    key = 50; 
  
    // Search the key using ternarySearch 
    p = ternarySearch(l, r, key, ar); 
  
    // Print the result 
    cout << "Index of " << key 
         << " is " << p << endl; 
} 
  
// This code is contributed 
// by Akanksha_Rai