From 0b7e6040564ab823feb08adc59dc6c99b464478c Mon Sep 17 00:00:00 2001
From: "Dr. Matthias Ratajczak" <m.ratajczak@hzdr.de>
Date: Fri, 19 Aug 2022 16:07:56 +0200
Subject: [PATCH] finish 20

---
 src/euler20/Cargo.toml  |  9 +++++++++
 src/euler20/src/main.rs | 19 +++++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 src/euler20/Cargo.toml
 create mode 100644 src/euler20/src/main.rs

diff --git a/src/euler20/Cargo.toml b/src/euler20/Cargo.toml
new file mode 100644
index 0000000..bcb8b7c
--- /dev/null
+++ b/src/euler20/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "euler20"
+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 = "*"
diff --git a/src/euler20/src/main.rs b/src/euler20/src/main.rs
new file mode 100644
index 0000000..1f5b5a8
--- /dev/null
+++ b/src/euler20/src/main.rs
@@ -0,0 +1,19 @@
+use gmp::mpz::Mpz;
+
+fn main() {
+    let x = faculty(Mpz::from(100));
+    let y: u32 = x
+        .to_string()
+        .chars()
+        .map(|c| c.to_digit(10).unwrap() as u32)
+        .sum();
+    println!("{y}");
+}
+
+fn faculty(x: Mpz) -> Mpz {
+    if x == Mpz::one() {
+        x
+    } else {
+        x.clone() * faculty(x - 1)
+    }
+}