
ZOJ Problem Set  4024
A sequence of $n$ integers $a_1, a_2, \dots, a_n$ is called a peak, if and only if there exists exactly one integer $k$ such that $1 < k < n$, and $a_i < a_{i+1}$ for all $1 \le i < k$, and $a_{i1} > a_i$ for all $k < i \le n$. Given an integer sequence, please tell us if it's a peak or not. InputThere are multiple test cases. The first line of the input contains an integer $T$, indicating the number of test cases. For each test case: The first line contains an integer $n$ ($3 \le n \le 10^5$), indicating the length of the sequence. The second line contains $n$ integers $a_1, a_2, \dots, a_n$ ($1 \le a_i \le 2 \times 10^9$), indicating the integer sequence. It's guaranteed that the sum of $n$ in all test cases won't exceed $10^6$. OutputFor each test case output one line. If the given integer sequence is a peak, output "Yes" (without quotes), otherwise output "No" (without quotes). Sample Input7 5 1 5 7 3 2 5 1 2 1 2 1 4 1 2 3 4 4 4 3 2 1 3 1 2 1 3 2 1 2 5 1 2 3 1 2 Sample OutputYes No No No Yes No No Author: WENG, Caizhi Source: The 15th Zhejiang Provincial Collegiate Programming Contest Sponsored by TuSimple 