Submission #68473579

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Source Code Expand

use std::collections::BTreeMap;

use ordered_float::OrderedFloat;
use proconio::input;

fn main() {
    input! {
        n: usize,
        xy: [(f64, f64); n],
    }

    let mut map_c = BTreeMap::new();
    let mut map_d = BTreeMap::new();
    for i in 0..n {
        let (xi, yi) = xy[i];
        for j in 0..n {
            let (xj, yj) = xy[j];
            let dx = xi - xj;
            let dy = yi - yj;
            if !(dx > 0.0 || (dx == 0.0 && dy > 0.0)) {
                continue;
            }
            let s = OrderedFloat::from(dy / dx);
            *map_c.entry(s).or_insert(0_u64) += 1;
            let mx = OrderedFloat::from(0.5 * (xi + xj));
            let my = OrderedFloat::from(0.5 * (yi + yj));
            *map_d.entry((mx, my)).or_insert(0_u64) += 1;
        }
    }

    let add: u64 = map_c.values().map(|&v| v * (v - 1) / 2).sum();
    let sub: u64 = map_d.values().map(|&v| v * (v - 1) / 2).sum();
    let res = add - sub;
    println!("{res}");
}

Submission Info

Judge Result