#C8087. Increasing Subsequence
Increasing Subsequence
Increasing Subsequence
Given a sequence of n integers, determine whether there exists a strictly increasing subsequence of length at least 3.
A strictly increasing subsequence is a sequence of indices i, j, k such that i < j < k and a[i] < a[j] < a[k]. In mathematical notation, we require that there exist indices \( 1 \leq i < j < k \leq n \) satisfying: \[ a[i] < a[j] < a[k] \]
If such a subsequence exists, output YES
; otherwise, output NO
.
inputFormat
The input is given from standard input and consists of two lines:
- The first line contains a single integer n (\(1 \le n \le 10^5\)), representing the number of elements in the sequence.
- The second line contains n space-separated integers \(a_1, a_2, \ldots, a_n\) where \(-10^9 \le a_i \le 10^9\).
outputFormat
Output a single line to standard output containing either YES
if there exists a strictly increasing subsequence of length at least 3, or NO
otherwise.
5
5 1 2 4 3
YES
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