added kadane's algorithm

Author: itsadityagupta

classical_algorithms/kadanes_algorithm.py

@@ -0,0 +1,24 @@
+'''
+Kadane's Algorithm is a standard technique used majorly for problems like:
+
+Given an integer array nums, find the contiguous subarray (containing at least one number) 
+which has the largest sum and return its sum.
+'''
+def kadanes_algorithm(nums):
+        max_ending_here = 0
+        max_so_far = float('-inf')
+        
+        for i in range(len(nums)):
+            max_ending_here = max_ending_here+nums[i]
+            max_so_far = max(max_so_far, max_ending_here)
+            
+            if max_ending_here < 0:
+                max_ending_here = 0
+            
+        return max_so_far
+
+nums = [-2,1,-3,4,-1,2,1,-5,4]
+print(kadanes_algorithm(nums)) # Output= 6
+
+nums = [-1]
+print(kadanes_algorithm(nums)) #output= -1