Problem:
Score : 300 points

Problem Statement

You are given an array A of length N.
Your task is to divide it into several contiguous subarrays.
Here, all subarrays obtained must be sorted in either non-decreasing or non-increasing order.
At least how many subarrays do you need to divide A into?

Constraints

1 \leq N \leq 10^5

1 \leq A_i \leq 10^9

Each A_i is an integer.

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 ... A_N

Output

Print the minimum possible number of subarrays after division of A.

Sample Input 1

6
1 2 3 2 2 1

Sample Output 1

2

One optimal solution is to divide the array into [1,2,3] and [2,2,1].

Sample Input 2

9
1 2 1 2 1 2 1 2 1

Sample Output 2

5

Sample Input 3

7
1 2 3 2 1 999999999 1000000000

Sample Output 3

3

Solution in Rust (1.15.1) (judge verdict: Accepted)

use std::io::{BufRead, Write};
use std::io;
use std::cmp::Ordering;

fn solve<R: BufRead, W: Write>(mut input: R, mut output: W) {
    let mut s = String::new();
    input.read_line(&mut s).unwrap();
    let mut split = s.split_whitespace();
    let _ = split.next().unwrap().parse::<usize>().unwrap();
    let mut s = String::new();
    input.read_line(&mut s).unwrap();
    let a = s.split_whitespace()
        .map(|s| s.parse::<u32>().unwrap())
        .collect::<Vec<_>>();
    let mut result = 1usize;
    if a.len() >= 2 {
        let mut flag = a[1].cmp(&a[0]);
        for i in 1..a.len() {
            match (a[i].cmp(&a[i - 1]), flag) {
                (x, y) if x == y => {}
                (Ordering::Equal, _) => {}
                (x, Ordering::Equal) => {
                    flag = x;
                }
                _ => {
                    result += 1;
                    if i != a.len() - 1 {
                        flag = a[i + 1].cmp(&a[i]);
                    }
                }
            }
        }
    }
    writeln!(output, "{}", result).unwrap();
}

fn main() {
    let stdin = io::stdin();
    let stdout = io::stdout();
    solve(stdin.lock(), stdout.lock());
}

#[cfg(test)]
mod tests {
    fn test(input: &str, output: &str) {
        let mut v = Vec::<u8>::new();
        ::solve(input.as_bytes(), &mut v);
        assert_eq!(String::from_utf8(v).unwrap(), output);
    }
    #[test]
    fn case1() {
        test("6
1 2 3 2 2 1\n",
             "2\n");
    }
    #[test]
    fn case2() {
        test("9
1 2 1 2 1 2 1 2 1\n",
             "5\n");
    }
    #[test]
    fn case3() {
        test("7
1 2 3 2 1 999999999 1000000000\n",
             "3\n");
    }
}