Pick from both sides!

Author: anantkaushik

Python/Interviewbit/Arrays/pick-from-both-sides.py

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+"""
+Problem Link: https://www.interviewbit.com/problems/pick-from-both-sides/
+
+Problem Description
+
+Given an integer array A of size N.
+You can pick B elements from either left or right end of the array A to get maximum sum.
+Find and return this maximum possible sum.
+NOTE: Suppose B = 4 and array A contains 10 elements then:
+You can pick first four elements or can pick last four elements or can pick 1 from front and 
+3 from back etc . you need to return the maximum possible sum of elements you can pick.
+
+Problem Constraints
+1 <= N <= 105
+1 <= B <= N
+-103 <= A[i] <= 103
+
+Input Format
+First argument is an integer array A.
+Second argument is an integer B.
+
+Output Format
+Return an integer denoting the maximum possible sum of elements you picked.
+
+Example Input
+Input 1:
+A = [5, -2, 3 , 1, 2]
+B = 3
+
+Input 2:
+A = [1, 2]
+B = 1
+
+Example Output
+Output 1:
+8
+
+Output 2:
+2
+
+Example Explanation
+Explanation 1:
+Pick element 5 from front and element (1, 2) from back so we get 5 + 1 + 2 = 8
+
+Explanation 2:
+Pick element 2 from end as this is the maximum we can get
+"""
+class Solution:
+    # @param A : list of integers
+    # @param B : integer
+    # @return an integer
+    def solve(self, A, B):
+        cur_sum = 0
+        for i in range(B):
+            cur_sum += A[i]
+            
+        if B == len(A):
+            return cur_sum
+            
+        max_sum = cur_sum
+        index = B-1
+        for i in range(len(A)-1, len(A)-B-1, -1):
+            cur_sum +=  (A[i] - A[index])
+            max_sum = max(max_sum, cur_sum)
+            index -= 1
+        return max_sum
+