Added Tree type and implementations

gemla/src/main.rs

@@ -1,3 +1,18 @@
-fn main() {
-    println!("Hello, world!");
+mod tree;
+
+fn build_tree(h: u32) -> Option<Box<tree::Tree>> {
+    let mut result: Option<Box<tree::Tree>> = None;
+
+    if h != 0 {
+        result = Some(tree::concat_trees(h, build_tree(h - 1), build_tree(h - 1)));
+    }
+
+    result
 }
+
+fn main() {
+    let tree: tree::Tree = *build_tree(25).expect("Error getting result from build tree.");
+
+    println!("Resulting tree from build_tree.");
+    println!("{}", tree);
+}

gemla/src/tree/mod.rs

@@ -0,0 +1,28 @@
+use std::fmt;
+
+pub struct Tree {
+    val: u32,
+    left: Option<Box<Tree>>,
+    right: Option<Box<Tree>>
+}
+
+pub fn concat_trees(v: u32, l: Option<Box<Tree>>, r: Option<Box<Tree>>) -> Box<Tree> {
+    Box::new(Tree {
+        val: v,
+        left: l,
+        right: r
+    })
+}
+
+impl fmt::Display for Tree {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let node_str = |t: &Option<Box<Tree>>| -> String {
+            match t {
+                Some(n) => format!("{}", *n),
+                _ => String::from("_")
+            }
+        };
+
+        write!(f, "({} :{}|{})", self.val, node_str(&self.left), node_str(&self.right))
+    }
+}