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HackerRank Solution – Problem Solving – Game of Two Stacks

Alexa has two stacks of non-negative integers, stack a[n] and stack b[m] where index 0 denotes the top of the stack. Alexa challenges Nick to play the following game:

  • In each move, Nick can remove one integer from the top of either stack a or stack b.
  • Nick keeps a running sum of the integers he removes from the two stacks.
  • Nick is disqualified from the game if, at any point, his running sum becomes greater than some integer maxSum given at the beginning of the game.
  • Nick’s final score is the total number of integers he has removed from the two stacks.

This article shows the solution of the interview preparation problem which is give by Hacker Rank. The Problem will also helps to improve your Data Structure skills,

Given a, b, and maxSum for g games, find the maximum possible score Nick can achieve.

a = [1, 2, 3, 4, 5]b = [6, 7, 8, 9]

The maximum number of values Nick can remove is 4. There are two sets of choices with this result.

  1. Remove 1, 2, 3, 4 from a with a sum of 10.
  2. Remove 1, 2, 3 from a and 6 from b with a sum of 12.

Function Description
Complete the twoStacks function in the editor below.

twoStacks has the following parameters: – int maxSum: the maximum allowed sum
– int a[n]: the first stack
– int b[m]: the second stack

– int: the maximum number of selections Nick can make

Input Format

The first line contains an integer, g (the number of games). The 3*g subsequent lines describe each game in the following format:

  1. The first line contains three space-separated integers describing the respective values of n (the number of integers in stack a), m (the number of integers in stack b),and maxSum (the number that the sum of the integers removed from the two stacks cannot exceed).
  2. The second line contains n space-separated integers, the respective values of a[i].
  3. The third line contains m space-separated integers, the respective values of b[i].


  • 1 <= g <= 50
  • 1 <= n,m <= 10^5
  • 0 <= a[i],b[i] <= 10^6
  • 1 <= maxSum <= 10^9


  • 1 <= n,m <= 100 for 50% of the maximum score.

Sample Input 0

5 4 10
4 2 4 6 1
2 1 8 5

Sample Output 0


Explanation 0

The two stacks initially look like this:


The image below depicts the integers Nick should choose to remove from the stacks. We print 4 as our answer, because that is the maximum number of integers that can be removed from the two stacks without the sum exceeding x=10.


(There can be multiple ways to remove the integers from the stack, the image shows just one of them.)


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