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TernarySearch.cpp
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TernarySearch.cpp
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#include <bits/stdc++.h>
using namespace std;
//Recursive Approach: Time Complexity Is O(log3(N))
int ternarySearchRecursion(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 ternarySearchRecursion(l, mid1 - 1, key, ar);
}
else if (key > ar[mid2]) {
// The key lies in between mid2 and r
return ternarySearchRecursion(mid2 + 1, r, key, ar);
}
else {
// The key lies in between mid1 and mid2
return ternarySearchRecursion(mid1 + 1, mid2 - 1, key, ar);
}
}
// Key not found
return -1;
}
//Iterative Approach: Time Complexity Is O(log3(N))
int ternarySearchIterative(int l, int r, int key, int ar[])
{
while (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
r = mid1 - 1;
}
else if (key > ar[mid2]) {
// The key lies in between mid2 and r
l = mid2 + 1;
}
else {
// The key lies in between mid1 and mid2
l = mid1 + 1;
r = mid2 - 1;
}
}
// Key not found
return -1;
}
int main()
{
int left, right, index, key;
cout<<"Enter Number Of Elements in the array:\n";
cin>>right;// length of array
int ar[right];
cout<<"Enter The Elements In Array:\n";
for(int i=0;i<right;i++){
cin>>ar[i];
}
left = 0;// Starting index
cout<<"Enter The Element To Be Searched:\n";
cin>>key;// Key to be searched in the array
index = ternarySearchIterative(left, right, key, ar);// Search the key using Iterative Ternary Search
cout << "Iterative Approach : Index of " << key << " is " << index << endl;
index = ternarySearchRecursion(left, right, key, ar); // Search the key using Recursive Ternary Search
cout << "Recursive Approach : Index of " << key << " is " << index << endl;
}
'''
Time Complexity : O(log3(N))
Sample I/O:
INPUT :
Enter Number Of Elements in the array:
9
Enter The Elements In Array:
1 2 3 4 5 6 7 8 9
Enter The Element To Be Searched:
5
OUTPUT :
Iterative Approach : Index of 5 is 4
Recursive Approach : Index of 5 is 4
'''