Suppose we have a sequence of non-negative integers, Namely a1, a2, ..., an. At each time we can choose one term ai with 0 < i < n and we subtract 1 from both ai and ai+1. We wonder whether we can get a sequence of all zeros after several operations.


The first line is the number of test cases T (0 < T <= 20).

The first line of each test case is a number N (0 < N <= 10000). The next line is N non-negative integers, 0 <= ai <= 109.


If it can be modified into all zeros with several operations output “YES” in a single line, otherwise output “NO” instead.


1 2
2 2



It is clear that [1 2] can be reduced to [0 1] but no further to convert all integers to 0. Hence, the output is NO.

In second case, output is YES as [2 2] can be reduced to [1 1] and then to [0 0] in just two steps.

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ameyanator: 2018-04-01 22:06:12

Okay so the test cases are extremly weak. And I wouldn't have even realized if it were not for the comments. Thanks all!
Be sure to run your code on
0 4 2 0 2
before moving on to the next question

venuraja1432: 2018-03-29 14:35:55

we can do this problem..... without using an array,ie O(1) space

venuraja1432: 2018-03-29 14:35:55

we can do this problem..... without using an array,ie O(1) space

prakash1108: 2018-01-15 16:47:42

size of array costed me many WAs

abhar10: 2017-12-26 18:00:55

AC in One Go !!
Easy One.

Last edit: 2017-12-26 18:05:53
sedulous_001: 2017-09-25 17:23:50

Wrong Test cases. It is not supposed to accept the sequence 0 4 2 0 2. As it is not possible to reduce down the sequence into the one with all entries zero. But it is accepting my code which accepts this sequence. :(
Simply calculating sum is not all the question wants. Correct me, if i'm wrong. :)

up79: 2017-06-18 11:29:56

think simple just do what question say :P

cake_is_a_lie: 2017-04-05 02:14:39

I wonder, what would constitute "strong" test cases? This is a very easy problem.

srnsh: 2017-01-12 15:05:51

Weak Test cases....wrong solution gets accepted.

kira28: 2016-12-08 14:48:06

AC in one go... !!
simple one

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