アルゴリズムと数学 035

https://atcoder.jp/contests/math-and-algorithm/tasks/math_and_algorithm_ag

半径と中心間の距離の関係ですね。

// Two Circles
#![allow(non_snake_case)]

use std::ops::Sub;


//////////////////// 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()
}


//////////////////// Point ////////////////////

#[derive(Clone, Copy)]
#[derive(Debug)]
struct Point {
    x: f64,
    y: f64,
}

impl Sub for Point {
    type Output = Self;
    
    fn sub(self, other: Self) -> Self {
        Self { x: self.x - other.x, y: self.y - other.y }
    }
}

impl Point {
    fn inner_product(v: &Point, w: &Point) -> f64 {
        v.x * w.x + v.y * w.y
    }
    
    fn mag(&self) -> f64 {
        Point::inner_product(self, self).sqrt()
    }
}


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

type Circle = (Point, f64);

fn read_input() -> Circle {
    let v = read_vec();
    (Point { x: v[0], y: v[1] }, v[2])
}

fn f(C1: Circle, C2: Circle) -> i32 {
    let d = (C1.0 - C2.0).mag();
    if C1.1 > C2.1 + d || C2.1 > C1.1 + d {
        1
    }
    else if C1.1 == C2.1 + d || C2.1 == C1.1 + d {
        2
    }
    else if C1.1 + C2.1 == d {
        4
    }
    else if C1.1 + C2.1 < d {
        5
    }
    else {
        3
    }
}

fn main() {
    let C1 = read_input();
    let C2 = read_input();
    println!("{}", f(C1, C2))
}