BOI7SEQ - Sequence

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We are given a sequence a1 , ..., an . We can manipulate this sequence using the operation reduce(i), which replaces elements ai and ai+1 with a single element max(ai , ai+1 ), resulting in a new shorter sequence. The cost of this operation is max(ai , ai+1 ). After n−1 operations reduce, we obtain a sequence of length 1. Our task is to compute the cost of the optimal reducing scheme, i.e. the sequence of reduce operations with minimal cost leading to a sequence of length 1.


The first line contains n (1 ≤ n ≤ 1,000,000), the length of the sequence. The following n lines contain one integer ai , the elements of the sequence (0 ≤ ai ≤ 1,000,000,000).


In the first and only line of the output print the minimal cost of reducing the sequence to a single element.


Output: 5

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nadstratosfer: 2019-03-28 08:25:58

Frustrating to crack, and in the end the stupid time limit makes this an input test: TLE in PyPy, 0.01s in CPP.

hello_world123: 2018-07-18 19:12:39

Good question !!!
Done in O(1) space and O(n) time .
Think greedily

Last edit: 2018-07-18 19:30:32
neha1824: 2018-07-07 21:00:15

I am getting correct output for all test cases at yet my solution is not getting accepted

Last edit: 2018-07-07 21:02:30
leoamish300: 2018-02-10 08:12:30

Don't be a fool. The input is NOT sorted always.

bhabya_brj: 2018-01-24 06:17:20

@akshayvenkat where is it specifed?

code_aim: 2017-10-20 22:12:02

Nice one!!

akshayvenkat: 2016-07-05 18:07:41

the input seems to be sorted always

minhthai: 2016-03-17 16:16:04

O(n) in java cannot pass, just need 0.5s more :(((

Added by:Race with time
Time limit:0.181s-0.362s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ASM64
Resource:Baltic Olympiad 2007