## C, search, ternary_search.c

#include <stdio.h>

// 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);
}
}

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
printf("Index of %d is %d\n", key, p);

// 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
printf("Index of %d is %d", key, p);
}