restructure; add challenge 2 solution

I forgot about atomic commits...

challenges/december-2024/c2/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "challenge-2"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+geometry = {path = "../../../lib/geometry" }
+
+

challenges/december-2024/c2/src/main.rs

@@ -0,0 +1,24 @@
+use geometry::{read_point, Triangle};
+
+fn read_triangle(name: &str) -> Triangle {
+    println!(
+        "Enter the coordinates for the three vertices of triangle {}:",
+        name
+    );
+    let p1 = read_point("First vertex (x y):");
+    let p2 = read_point("Second vertex (x y):");
+    let p3 = read_point("Third vertex (x y):");
+
+    Triangle { p1, p2, p3 }
+}
+
+fn main() {
+    let triangle1 = read_triangle("1");
+    let triangle2 = read_triangle("2");
+
+    if triangle1.overlaps(&triangle2) {
+        println!("The two triangles overlap.");
+    } else {
+        println!("The two triangles do not overlap.");
+    }
+}