From a4dda171b5f81f900e4d617b08ae8c0e2d374e37 Mon Sep 17 00:00:00 2001
From: Sijmen Schoon <me@sijmenschoon.nl>
Date: Sat, 26 Dec 2020 00:19:07 +0100
Subject: [PATCH] rust(day06): yee

---
 rust/src/day06.rs | 41 +++++++++++++++++++++++++++++++++++++++++
 rust/src/main.rs  |  2 +-
 2 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 rust/src/day06.rs

diff --git a/rust/src/day06.rs b/rust/src/day06.rs
new file mode 100644
index 0000000..45dd10b
--- /dev/null
+++ b/rust/src/day06.rs
@@ -0,0 +1,41 @@
+use std::time::{Duration, Instant};
+
+fn count_bits(i: u32) -> u32 {
+    let i = i - ((i >> 1) & 0x55555555);
+    let i = (i & 0x33333333) + ((i >> 2) & 0x33333333);
+    (((i + (i >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24
+}
+
+pub fn run(print: bool) -> Duration {
+    let file_string = std::fs::read_to_string("../inputs/06").unwrap();
+    let instant = Instant::now();
+
+    let mut part1 = 0;
+    let mut part2 = 0;
+
+    for group in file_string.trim().split("\n\n") {
+        let mut set = 0u32;
+        for c in group.chars().filter(|c| c.is_alphabetic()) {
+            set |= 1 << (c as usize - 'a' as usize);
+        }
+        part1 += count_bits(set);
+
+        let mut line_set = 0u32;
+        for c in group.chars() {
+            if c == '\n' {
+                set &= line_set;
+                line_set = 0;
+            } else {
+                line_set |= 1 << (c as usize - 'a' as usize);
+            }
+        }
+        set &= line_set;
+        part2 += count_bits(set);
+    }
+
+    if print {
+        dbg!(part1, part2);
+    }
+
+    instant.elapsed()
+}
diff --git a/rust/src/main.rs b/rust/src/main.rs
index efad8b2..896ce08 100644
--- a/rust/src/main.rs
+++ b/rust/src/main.rs
@@ -7,7 +7,7 @@ mod day02;
 mod day03;
 mod day04;
 mod day05;
-use nop as day06;
+mod day06;
 use nop as day07;
 mod day08;
 mod day09;