AtCoder Beginner Contest 369 D

https://atcoder.jp/contests/abc369/tasks/abc369_d

単なるDPです。

// Bonus EXP
#![allow(non_snake_case)]


//////////////////// library ////////////////////

fn read<T: std::str::FromStr>() -> T {
    let mut line = String::new();
    std::io::stdin().read_line(&mut line).ok();
    line.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>().split_whitespace()
            .map(|e| e.parse().ok().unwrap()).collect()
}


//////////////////// process ////////////////////

fn read_input() -> Vec<i64> {
    let _N: usize = read();
    let A: Vec<i64> = read_vec();
    A
}

type DP = (i64, i64);

use std::cmp::max;

fn update_DP(a: i64, dp: DP) -> DP {
    (max(dp.0, dp.1 + a * 2), max(dp.0 + a, dp.1))
}

fn F(A: Vec<i64>) -> i64 {
    let N = A.len();
    let mut dp: DP = (0, A[0]);
    for i in 1..N {
        dp = update_DP(A[i], dp)
    }
    max(dp.0, dp.1)
}

fn main() {
    let A = read_input();
    println!("{}", F(A))
}