From b3f9c09f44cc6da6a85a4b8f8e3db3eaeaedf577 Mon Sep 17 00:00:00 2001
From: Mariano <rfmariano@protonmail.com>
Date: Sun, 4 Aug 2024 16:37:26 +0200
Subject: [PATCH] Wrote program for Day 10

https://en.wikipedia.org/wiki/Catalan_number
---
 .../day10/Cargo.toml                          |  6 +++++
 .../day10/src/lib.rs                          |  9 +++++++
 .../day10/src/main.rs                         | 24 +++++++++++++++++++
 .../day10/tests/example.rs                    | 14 +++++++++++
 4 files changed, 53 insertions(+)
 create mode 100644 Week-02/Day-10_Unique-Binary-Search-Trees/day10/Cargo.toml
 create mode 100644 Week-02/Day-10_Unique-Binary-Search-Trees/day10/src/lib.rs
 create mode 100644 Week-02/Day-10_Unique-Binary-Search-Trees/day10/src/main.rs
 create mode 100644 Week-02/Day-10_Unique-Binary-Search-Trees/day10/tests/example.rs

diff --git a/Week-02/Day-10_Unique-Binary-Search-Trees/day10/Cargo.toml b/Week-02/Day-10_Unique-Binary-Search-Trees/day10/Cargo.toml
new file mode 100644
index 0000000..3c916ef
--- /dev/null
+++ b/Week-02/Day-10_Unique-Binary-Search-Trees/day10/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "day10"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/Week-02/Day-10_Unique-Binary-Search-Trees/day10/src/lib.rs b/Week-02/Day-10_Unique-Binary-Search-Trees/day10/src/lib.rs
new file mode 100644
index 0000000..4c3d0a9
--- /dev/null
+++ b/Week-02/Day-10_Unique-Binary-Search-Trees/day10/src/lib.rs
@@ -0,0 +1,9 @@
+pub fn catalan_number(n: u8) -> usize {
+    let mut result = 1f64;
+
+    for k in 2..=n {
+        result *= (n as f64 + k as f64) / k as f64;
+    }
+
+    result.round() as usize
+}
diff --git a/Week-02/Day-10_Unique-Binary-Search-Trees/day10/src/main.rs b/Week-02/Day-10_Unique-Binary-Search-Trees/day10/src/main.rs
new file mode 100644
index 0000000..a27f306
--- /dev/null
+++ b/Week-02/Day-10_Unique-Binary-Search-Trees/day10/src/main.rs
@@ -0,0 +1,24 @@
+use std::io::{self, Write};
+
+use day10::catalan_number;
+
+fn main() {
+    let mut buffer = String::new();
+
+    print!("Insert n: ");
+    io::stdout().flush().expect("Failed to flush stdout.");
+
+    io::stdin()
+        .read_line(&mut buffer)
+        .expect("Failed to read from stdin.");
+
+    let n: u8 = buffer
+        .trim()
+        .parse()
+        .expect("The input is not a positive integer");
+
+    println!(
+        "The number of structurally unique BST's that store values from 1 to n is {}",
+        catalan_number(n)
+    );
+}
diff --git a/Week-02/Day-10_Unique-Binary-Search-Trees/day10/tests/example.rs b/Week-02/Day-10_Unique-Binary-Search-Trees/day10/tests/example.rs
new file mode 100644
index 0000000..797470f
--- /dev/null
+++ b/Week-02/Day-10_Unique-Binary-Search-Trees/day10/tests/example.rs
@@ -0,0 +1,14 @@
+use day10::catalan_number;
+
+#[test]
+fn example() {
+    assert_eq!(catalan_number(3), 5);
+}
+
+#[test]
+fn examplu() {
+    let array = [1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, 58786];
+    for (i, a) in array.into_iter().enumerate() {
+        assert_eq!(catalan_number(i as u8), a);
+    }
+}