From b1a8ab8bcdb43ad282af80189763476f3ac427f2 Mon Sep 17 00:00:00 2001
From: Joseph Montanaro <jfmontanaro@modg.org>
Date: Fri, 3 Dec 2021 14:48:34 -0800
Subject: [PATCH] refactor in preparation for part 2

---
 2021/src/day3.rs | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/2021/src/day3.rs b/2021/src/day3.rs
index 4902b93..51189e2 100644
--- a/2021/src/day3.rs
+++ b/2021/src/day3.rs
@@ -1,7 +1,7 @@
 use color_eyre::eyre;
 
 
-pub fn part1(numbers: &Vec<u16>) -> u64 {
+fn most_common_bits(numbers: &Vec<u16>) -> u16 {
     let mut bit_diffs: [isize; 12] = [0; 12];
     for num in numbers {
         for i in 0..11 {
@@ -14,13 +14,24 @@ pub fn part1(numbers: &Vec<u16>) -> u64 {
         }
     }
 
-    let mut gamma = 0u16;
+    let mut result = 0u16;
     for (i, sum) in bit_diffs.iter().enumerate() {
         let bit = if *sum >= 0 {1} else {0};
-        gamma |= bit << i;
+        result |= bit << i;
     }
 
-    let epsilon = !gamma & (65535 >> 4); // since these are really only 12-bit numbers we have to clear the 4 spurious 1's that come from inverting epsilon
+    result
+}
+
+
+fn invert_12bit(n: u16) -> u16 {
+    !n & (65535 >> 4) // since these are really only 12-bit numbers we have to clear the 4 spurious 1's that come from inverting the original
+}
+
+
+fn part1(numbers: &Vec<u16>) -> u64 {
+    let gamma = most_common_bits(numbers);
+    let epsilon = invert_12bit(gamma);
     epsilon as u64 * gamma as u64
 }