TWENDS - Two Ends

In the two-player game “Two Ends”, an even number of cards is laid out in a row. On each card, face up, is written a positive integer. Players take turns removing a card from either end of the row and placing the card in their pile. The player whose cards add up to the highest number wins the game. Now one strategy is to simply pick the card at the end that is the largest — we’ll call this the greedy strategy. However, this is not always optimal, as the following example shows: (The first player would win if she would first pick the 3 instead of the 4.)

3 2 10 4

You are to determine exactly how bad the greedy strategy is for different games when the second player uses it but the first player is free to use any strategy she wishes.


There will be multiple test cases. Each test case will be contained on one line. Each line will start with an even integer n followed by n positive integers. A value of n = 0 indicates end of input. You may assume that n is no more than 1000. Furthermore, you may assume that the sum of the numbers in the list does not exceed 1,000,000.


For each test case you should print one line of output of the form:

In game m, the greedy strategy might lose by as many as p points.

where m is the number of the game (starting at game 1) and p is the maximum possible difference between the first player’s score and second player’s score when the second player uses the greedy strategy. When employing the greedy strategy, always take the larger end. If there is a tie, remove the left end.


4 3 2 10 4
8 1 2 3 4 5 6 7 8
8 2 2 1 5 3 8 7 3

In game 1, the greedy strategy might lose by as many as 7 points.
In game 2, the greedy strategy might lose by as many as 4 points.
In game 3, the greedy strategy might lose by as many as 5 points.

hide comments
wewark: 2016-08-08 21:07:53

got a WA for "by" -.-

pvsmpraveen: 2016-07-03 14:06:02

Loved Solving ;)

Harish Chandra Thuwal: 2016-06-23 20:25:13

The question must specify that during greedy if tie occurs one must remove from left end -__-

singh1495: 2016-06-19 08:51:00

easy dp similer to TRT but onr tricky case that if there are same both end than chosse first-one...

Subhendu Sethi: 2016-05-20 19:42:58

SOLVED in one GO using recursion+memo!
But how to find the sequence of 2nd player.

Rudra Nil Basu: 2016-04-24 17:45:19

AC in the first try! :D
Easy, but huge confidence booster :D

lakshay_v06: 2016-01-27 13:28:11

Easy! :) IMP => " If there is a tie, remove the left end. "

anuj0503: 2016-01-12 19:56:13

Hint: Just need to find sum of the array plus use dp for optimal soln.

bunnycoder: 2015-12-15 08:59:53

mind the dot at the end of the sentence
exactly the same question:

kejriwal: 2015-09-16 12:03:56

sweet easy dp !! :)

Added by:Camilo Andrés Varela León
Time limit:0.100s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ERL JS-RHINO NODEJS PERL6 VB.NET
Resource:East Central North America 2005