アルゴリズムと数学 034

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

総当たりでOKですね。
f64はminを取るのが面倒で、foldを使えば可能ですが、

fold(f64::MAX, f64::min)

がAtCoderでは通らなくて、f64::MAXの代わりに1e7としました。

// Nearest Points
#![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 read() -> Point {
        let v = read_vec();
        Point { x: v[0], y: v[1] }
    }
    
    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 ////////////////////

fn read_input() -> Vec<Point> {
    let N: usize = read();
    (0..N).map(|_| Point::read()).collect::<Vec<Point>>()
}

fn f(pts: Vec<Point>) -> f64 {
    let N = pts.len();
    (0..N).map(|i| (i+1..N).map(|j| (pts[i] - pts[j]).mag()).
                                    fold(1e7, f64::min)).
                                    fold(1e7, f64::min)
//                                  fold(f64::MAX, f64::min)).
//                                  fold(f64::MAX, f64::min)
}

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