2022-11-18：给定一个数组arr，表示连续n天的股价，数组下标表示第几天指标X：任意两天的股价之和 - 此两天间隔的天数

fn main() {
    let mut nums = vec![2, 3, 1, 4, 0];
    let ans = max_x(&mut nums);
    println!("ans = {:?}", ans);
}

fn max_x(arr: &mut Vec<i32>) -> i32 {
    if arr.len() < 2 {
        return -1;
    }
    // 0 + arr[0]
    let mut pre_best = arr[0];
    let mut ans = 0;
    for i in 1..arr.len() as i32 {
        ans = get_max(ans, arr[i as usize] - i + pre_best);
        pre_best = get_max(pre_best, arr[i as usize] + i);
    }
    return ans;
}

fn get_max<T: Clone + Copy + std::cmp::PartialOrd>(a: T, b: T) -> T {
    if a > b {
        a
    } else {
        b
    }
}