From 6fa6ab62e69148533ec02869225d357166dc65c8 Mon Sep 17 00:00:00 2001
From: "Dr. Matthias Ratajczak" <m.ratajczak@hzdr.de>
Date: Fri, 19 Aug 2022 15:45:35 +0200
Subject: [PATCH] finish 15

---
 src/euler15/Cargo.toml  | 12 ++++++++++++
 src/euler15/src/main.rs | 21 +++++++++++++++++++++
 2 files changed, 33 insertions(+)
 create mode 100644 src/euler15/Cargo.toml
 create mode 100644 src/euler15/src/main.rs

diff --git a/src/euler15/Cargo.toml b/src/euler15/Cargo.toml
new file mode 100644
index 0000000..92926da
--- /dev/null
+++ b/src/euler15/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "euler15"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rust-gmp = "*"
+
+[profile.release]
+lto = true
diff --git a/src/euler15/src/main.rs b/src/euler15/src/main.rs
new file mode 100644
index 0000000..b920d75
--- /dev/null
+++ b/src/euler15/src/main.rs
@@ -0,0 +1,21 @@
+use gmp::mpz::Mpz;
+
+const LENGTH: usize = 20;
+fn main() {
+    for i in 1..=LENGTH {
+        let i = Mpz::from(i as u32);
+        print!("{i} x {i}: ");
+
+        let divisor = faculty(i.clone());
+        let result = faculty(Mpz::from(2) * i) / (divisor.clone() * divisor);
+        println!("{}", result);
+    }
+}
+
+fn faculty(x: Mpz) -> Mpz {
+    if x == Mpz::one() {
+        x
+    } else {
+        x.clone() * faculty(x - 1)
+    }
+}