From 471a3064adfa47d8d6c9161e3312f1a043179595 Mon Sep 17 00:00:00 2001
From: dece <shgck@pistache.land>
Date: Sun, 7 Nov 2021 20:43:59 +0100
Subject: [PATCH] 2015 day 11

---
 2015/src/bin/day11.rs | 75 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 2015/src/bin/day11.rs

diff --git a/2015/src/bin/day11.rs b/2015/src/bin/day11.rs
new file mode 100644
index 0000000..99b1433
--- /dev/null
+++ b/2015/src/bin/day11.rs
@@ -0,0 +1,75 @@
+use aoc::input;
+
+fn main() {
+    let mut pass = input::read_chars();
+
+    // Part 1
+    get_next_pass(&mut pass);
+    println!("Next pass: {}", pass);
+
+    // Part 2
+    get_next_pass(&mut pass);
+    println!("Next pass: {}", pass);
+}
+
+fn get_next_pass(pass: &mut String) {
+    loop {
+        unsafe { inc(pass.as_bytes_mut()) }
+        let pb = pass.as_bytes();
+        if has_seq(pb) && !has_banned_chars(pb) && has_pairs(&pass) {
+            break;
+        }
+    }
+}
+
+fn has_seq(pass: &[u8]) -> bool {
+    for i in 0..(pass.len() - 2) {
+        if pass[i] == pass[i + 1] - 1 && pass[i + 1] == pass[i + 2] - 1 {
+            return true;
+        }
+    }
+    false
+}
+
+fn has_banned_chars(pass: &[u8]) -> bool {
+    for b in b"iol".iter() {
+        if pass.contains(b) {
+            return true;
+        }
+    }
+    false
+}
+
+fn has_pairs(pass: &str) -> bool {
+    let mut num_pairs = 0;
+    let mut pc = ' ';
+    let mut skip_next = false;
+    for c in pass.chars() {
+        if skip_next {
+            skip_next = false;
+            pc = c;
+            continue
+        }
+        if c == pc {
+            num_pairs += 1;
+            skip_next = true;
+        }
+        pc = c;
+    }
+    num_pairs >= 2
+}
+
+fn inc(pass: &mut [u8]) {
+    let mut i = pass.len() - 1;
+    loop {
+        let lc = pass[i];
+        if lc < b'z' {
+            let offset = if lc == b'i' || lc == b'o' || lc == b'l' { 2 } else { 1 };
+            pass[i] = pass[i] + offset;
+            break;
+        } else {
+            pass[i] = b'a';
+            i -= 1;
+        }
+    }
+}