restructure; add challenge 2 solution

I forgot about atomic commits...

challenges/december-2024/c1/src/main.rs

@@ -0,0 +1,28 @@
+use geometry::{read_point, Triangle};
+fn main() {
+    // Read the vertices of the triangle we are calculating the area for.
+    let p1 = read_point("Enter the coordinates for the first vertex of the triangle (x y):");
+    let p2 = read_point("Enter the coordinates for the second vertex of the triangle (x y):");
+    let p3 = read_point("Enter the coordinates for the third vertex of the triangle (x y):");
+
+    // 'Draw' the triangle.
+    let triangle = Triangle { p1, p2, p3 };
+
+    // Read the point we want to test from user input.
+    // TODO: maybe some kind of input validation/loop would be nice
+    let test_point = read_point("Enter the coordinates for the point to test (x y):");
+
+    // Finally, check if the point is inside the triangle.
+    // TODO: make this a match
+    if triangle.contains_point(&test_point) {
+        println!(
+            "The point ({}, {}) lies inside the triangle.",
+            test_point.x, test_point.y
+        );
+    } else {
+        println!(
+            "The point ({}, {}) lies outside the triangle.",
+            test_point.x, test_point.y
+        );
+    }
+}