From fe45473e56f0c6deb830d59ce90bdea0469c16af Mon Sep 17 00:00:00 2001
From: timeshifter <timeshifter@altaica>
Date: Mon, 24 Mar 2025 14:20:06 +0100
Subject: [PATCH] 44

---
 src/euler44/Cargo.toml  |  7 +++++++
 src/euler44/src/main.rs | 21 +++++++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 src/euler44/Cargo.toml
 create mode 100644 src/euler44/src/main.rs

diff --git a/src/euler44/Cargo.toml b/src/euler44/Cargo.toml
new file mode 100644
index 0000000..9ca4b85
--- /dev/null
+++ b/src/euler44/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "euler44"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+itertools = "0.14.0"
diff --git a/src/euler44/src/main.rs b/src/euler44/src/main.rs
new file mode 100644
index 0000000..1b0ff95
--- /dev/null
+++ b/src/euler44/src/main.rs
@@ -0,0 +1,21 @@
+use itertools::Itertools;
+
+fn main() {
+    let pentagonals: Vec<_> = (1..10000).map(pentagonal_number).collect();
+    let combinations: Vec<_> = pentagonals.iter().combinations(2).collect();
+
+    for item in combinations {
+        let smaller = *item.first().unwrap();
+        let larger = *item.get(1).unwrap();
+        let sum = smaller + larger;
+        let difference = larger - smaller;
+        if pentagonals.contains(&sum) && pentagonals.contains(&difference) {
+            println!("{difference}");
+            break;
+        }
+    }
+}
+
+fn pentagonal_number(n: usize) -> usize {
+    n * (3 * n - 1) / 2
+}