From 863f051f7ddbb871a50af0285b796b5531817cd0 Mon Sep 17 00:00:00 2001
From: Philippe Zwietering <philippe.zwietering@gmail.com>
Date: Mon, 26 Jun 2023 15:38:35 +0200
Subject: [PATCH] Finished PE 091, fairly straightforward, just brute-forced

---
 projecteuler/091/Cargo.toml  |  8 ++++++++
 projecteuler/091/src/main.rs | 40 ++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 projecteuler/091/Cargo.toml
 create mode 100644 projecteuler/091/src/main.rs

diff --git a/projecteuler/091/Cargo.toml b/projecteuler/091/Cargo.toml
new file mode 100644
index 0000000..fca4e93
--- /dev/null
+++ b/projecteuler/091/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "main"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/projecteuler/091/src/main.rs b/projecteuler/091/src/main.rs
new file mode 100644
index 0000000..85a7170
--- /dev/null
+++ b/projecteuler/091/src/main.rs
@@ -0,0 +1,40 @@
+use std::collections::HashSet;
+use std::time::Instant;
+
+// Als het goed is, is dit te brute-forcen. Er zijn namelijk 50^4 permutaties van coordinaten,
+// want ieder coordinaat is twee cijfers (x,y) met 0 < x, y <= 50. Dit blijft in de miljoenen
+// hangen dus gegeven een O(1) check kun je dat best snel uitrekenen zonder slim te doen.
+
+fn check_right_triangle(a: &(u32, u32), b: &(u32, u32)) -> bool {
+    let po = a.0 * a.0 + a.1 * a.1;
+    let qo = b.0 * b.0 + b.1 * b.1;
+    let pq = (a.0 - b.0).pow(2) + (a.1 - b.1).pow(2);
+
+    let mut lengths = vec![po, qo, pq];
+    lengths.sort();
+    
+    return lengths[0] + lengths[1] == lengths[2] && a.0 * b.1 != a.1 * b.0;
+}
+
+fn main() {
+    println!("Hello, this is Patrick!");
+    let now = Instant::now();
+    
+    const COORD_MAX: u32 = 50;
+
+    let mut found_coordinates = HashSet::new();
+    for a_x in 0..=COORD_MAX {
+        for a_y in 0..=COORD_MAX {
+            for b_x in a_x..=COORD_MAX {
+                for b_y in 0..=a_y {
+                    if check_right_triangle(&(a_x, a_y), &(b_x, b_y)) {
+                        found_coordinates.insert(((a_x, a_y), (b_x, b_y)));
+                    }
+                }
+            }
+        }
+    }
+
+    println!("Number of triangles: {}", found_coordinates.len());
+    println!("Time passed: {:?}", Instant::now() - now);
+}