Refactor D4P2 in Rust

2019/04/src/main.rs

@@ -2,23 +2,23 @@
 use itertools::Itertools;
 
 pub fn main() {
-    let (lower, upper) = (172930, 683082);
+    let (lower, upper) = (172_930, 683_082);
     let valid_part1 = (lower..upper)
         .map(|n| n.to_string().chars().collect::<Vec<_>>())
         .filter(|n| n.is_sorted())
         .filter(|v| v.clone().iter().dedup().count() != v.len());
     println!("Part 1: {}", valid_part1.clone().count());
+
     let part2 = valid_part1
-        .filter(|v| {
-            let (mut last, mut streak, mut double) = (' ', 0, false);
-            v.iter().for_each(|c| {
-                if streak == 2 && c != &last {
-                    double = true
-                }
-                streak = if c == &last { streak + 1 } else { 1 };
-                last = *c;
-            });
-            double || streak == 2
+        .filter(|vec| {
+            vec.iter()
+                .group_by(move |n| *n)
+                .into_iter()
+                .filter_map(|(_, v)| if v.count() == 2 { Some(true) } else { None })
+                // can’t do this because I’m too smol brained for the borrow checker
+                //.filter(|(_, v)| v.count() == 2)
+                .count()
+                > 0
         })
         .count();
     println!("Part 2: {}", part2);