2022-06-02：一开始在0位置，每一次都可以向左或者向右跳，第i次能向左或者向右跳严格的i步。请问从0到x位置，至少跳几次

fn main() {
    let ans = reach_number(9);
    println!("ans = {}", ans);
}

fn reach_number(mut target: isize) -> isize {
    if target == 0 {
        return 0;
    }
    target = abs(target);
    let mut l: isize = 0;
    let mut r = target;
    let mut m:isize = 0;
    let mut near = 0;
    while l <= r {
        m = (l + r) / 2;
        if sum(m) >= target {
            near = m;
            r = m - 1;
        } else {
            l = m + 1;
        }
    }
    if sum(near) == target {
        return near;
    }
    if ((sum(near) - target) & 1) == 1 {
        near += 1;
    }
    if ((sum(near) - target) & 1) == 1 {
        near += 1;
    }
    return near;
}

fn sum(n: isize) -> isize {
    return (n * (n + 1)) / 2;
}

fn abs(a: isize) -> isize {
    if a < 0 {
        -a
    } else {
        a
    }
}