Merge pull request shivangdubey#272 from Aanchi-glitch2744/patch-1

Ternary Search algorithm in python

Author: shivangdubey

Diff for: python/Ternary_Search.py

@@ -0,0 +1,57 @@
+"""
+This is a type of divide and conquer algorithm which divides the search space into
+3 parts and finds the target value based on the property of the array or list
+(usually monotonic property).
+
+Time Complexity  : O(log3 N)
+Space Complexity : O(1)
+"""
+
+def ternary_search(ar, l, r, key): 
+  
+    if (r >= l): 
+        # Find the mid1 and mid2 
+        mid1 = l + (r - l) //3
+        mid2 = r - (r - l) //3
+         
+        if (ar[mid1] == key):  
+            return mid1 
+        if (ar[mid2] == key):  
+            return mid2 
+            
+        if (key < ar[mid1]):  
+            # The key lies in between l and mid1
+            r = mid1 - 1
+            return ternary_search(ar, l, r, key) 
+ 
+        elif (key > ar[mid2]):  
+            # The key lies in between mid2 and r
+            l = mid2 + 1
+            return ternary_search(ar, l, r, key) 
+          
+        else:  
+            # The key lies in between mid1 and mid2
+            l = mid1 + 1
+            r = mid2 - 1
+            return ternary_search(ar, l, r, key) 
+          
+    return -1
+
+# Driver Code
+arr = [int(item) for item in input("Enter the array elements : ").split()]
+key = int(input("Enter the number to be searched : "))
+arr.sort()
+l = 0
+r = len(arr) - 1
+print("Index of number is :",ternary_search(arr, l, r, key))
+
+"""
+Sample I/O :
+
+Input :
+Enter the array elements : 1 2 3 4 5                                                                                          
+Enter the number to be searched : 3
+
+Output :
+Index of key is : 2
+"""