peuler 0.1.0

A Rust crate with solutions to the Project Euler problems
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51

use crate::Solution;
use pmath::linalg::{Point, Vector};
use std::f64::consts::PI;

problem!(Problem0102, 102, "Triangle Containment");

impl Solution for Problem0102 {
    fn solve(&self) -> String {
        const INPUT: &str = include_str!("0102_triangles.txt");
        let triangles: Vec<[Point<2>; 3]> = INPUT
            .trim()
            .lines()
            .map(|line| {
                let mut line_iter = line
                    .trim()
                    .split(',')
                    .map(|num_str| num_str.parse::<f64>().unwrap());
                [
                    Point::new([line_iter.next().unwrap(), line_iter.next().unwrap()]),
                    Point::new([line_iter.next().unwrap(), line_iter.next().unwrap()]),
                    Point::new([line_iter.next().unwrap(), line_iter.next().unwrap()]),
                ]
            })
            .collect();

        // for every triangle, generate vectors from origin to each point
        // calculate and sum the angles between each vector
        // if the sum is 2pi, the triangle contains the origin
        // if the point is outside the triangle, the sum will be less than 2pi
        // count the number of triangles that contain the origin

        let mut count = 0;

        for triangle in triangles {
            let mut angle_sum = 0.0;
            let vec1 = Vector::from_points(Point::new([0.0; 2]), triangle[0]);
            let vec2 = Vector::from_points(Point::new([0.0; 2]), triangle[1]);
            let vec3 = Vector::from_points(Point::new([0.0; 2]), triangle[2]);

            angle_sum += vec1.angle_between(&vec2);
            angle_sum += vec2.angle_between(&vec3);
            angle_sum += vec3.angle_between(&vec1);

            if (angle_sum - 2.0 * PI).abs() < 1e-8 {
                count += 1;
            }
        }

        count.to_string()
    }
}