From 82a2bfd9d6e1fce06337bc38a9d460be26efe01a Mon Sep 17 00:00:00 2001
From: foosinn <stefan@f2o.io>
Date: Sun, 14 Jun 2020 11:24:43 +0200
Subject: [PATCH] day16

---
 Cargo.toml        |   4 ++
 input16           |   1 +
 src/day16/lost.rs |  32 ++++++++++++
 src/day16/main.rs | 122 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 159 insertions(+)
 create mode 100644 input16
 create mode 100644 src/day16/lost.rs
 create mode 100644 src/day16/main.rs

diff --git a/Cargo.toml b/Cargo.toml
index 32204e2..a6a9d81 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -58,3 +58,7 @@ path = "src/day14/main.rs"
 [[bin]]
 name = "day15"
 path = "src/day15/main.rs"
+
+[[bin]]
+name = "day16"
+path = "src/day16/main.rs"
diff --git a/input16 b/input16
new file mode 100644
index 0000000..1c2f915
--- /dev/null
+++ b/input16
@@ -0,0 +1 @@
+59713137269801099632654181286233935219811755500455380934770765569131734596763695509279561685788856471420060118738307712184666979727705799202164390635688439701763288535574113283975613430058332890215685102656193056939765590473237031584326028162831872694742473094498692690926378560215065112055277042957192884484736885085776095601258138827407479864966595805684283736114104361200511149403415264005242802552220930514486188661282691447267079869746222193563352374541269431531666903127492467446100184447658357579189070698707540721959527692466414290626633017164810627099243281653139996025661993610763947987942741831185002756364249992028050315704531567916821944
\ No newline at end of file
diff --git a/src/day16/lost.rs b/src/day16/lost.rs
new file mode 100644
index 0000000..6d26924
--- /dev/null
+++ b/src/day16/lost.rs
@@ -0,0 +1,32 @@
+// baesed on the idear of an recurring pattern
+// not required for the day 16 task
+
+struct EnumeratedCycle {
+    pattern: Vec<i64>,
+    position: usize,
+    iteration: usize,
+}
+
+impl EnumeratedCycle {
+    fn new(pattern: Vec<i64>, start: usize) -> Self {
+        Self {
+            pattern,
+            position: 0,
+            iteration: start,
+        }
+    }
+}
+
+impl Iterator for EnumeratedCycle {
+    type Item = (usize, i64);
+    fn next(&mut self) -> Option<Self::Item> {
+        let item = self.pattern.get(self.position)?;
+        let iteration = self.iteration;
+        self.position += 1;
+        if self.position == self.pattern.len() {
+            self.position = 0;
+            self.iteration += 1;
+        }
+        Some((iteration, *item))
+    }
+}
diff --git a/src/day16/main.rs b/src/day16/main.rs
new file mode 100644
index 0000000..6cc3ffd
--- /dev/null
+++ b/src/day16/main.rs
@@ -0,0 +1,122 @@
+use std::fs::File;
+use std::io::prelude::*;
+use std::iter;
+
+fn main() {
+    /*
+    let pattern = EnumeratedCycle::new(vec![0, 1, 0, -1], 1);
+    let pattern = pattern
+        .map(|(iteration, item)| iter::repeat(item).take(iteration))
+        .flatten();
+    */
+
+    // part 1
+    let f = File::open("input16").expect("unable to load \"input16\"");
+    let transmission: Vec<_> = f.bytes().map(|b| (b.unwrap() - b'0') as i64).collect();
+    print!("output: ");
+    phase_n(transmission, 100)
+        .iter()
+        .take(8)
+        .for_each(|i| print!("{}", i));
+    println!();
+}
+
+fn phase_n(input: Vec<i64>, phases: usize) -> Vec<i64> {
+    let mut output = input;
+    for _ in 0..phases {
+        output = phase(output)
+    }
+    output
+}
+
+fn phase(input: Vec<i64>) -> Vec<i64> {
+    let mut output: Vec<i64> = Vec::with_capacity(input.len());
+    for (pos, _) in input.iter().enumerate() {
+        let mut pattern = repeated_cycle(vec![0, 1, 0, -1], pos + 1);
+        pattern.next();
+        let mut value =
+            input
+                .iter()
+                .zip(pattern)
+                .map(|(a, b)| (a * b) % 10)
+                .fold(0, |i, mut acc| {
+                    acc += i;
+                    acc
+                });
+        if value < 0 {
+            value *= -1
+        }
+        output.push(value % 10);
+    }
+    output
+}
+
+fn repeated_cycle(input: Vec<i64>, repeats: usize) -> impl Iterator<Item = i64> {
+    input
+        .clone()
+        .into_iter()
+        .map(move |item| iter::repeat(item).take(repeats))
+        .flatten()
+        .cycle()
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn example1() {
+        assert_eq!(
+            phase(vec![1, 2, 3, 4, 5, 6, 7, 8]),
+            vec![4, 8, 2, 2, 6, 1, 5, 8]
+        );
+        assert_eq!(
+            phase(vec![4, 8, 2, 2, 6, 1, 5, 8]),
+            vec![3, 4, 0, 4, 0, 4, 3, 8]
+        );
+        assert_eq!(
+            phase(vec![3, 4, 0, 4, 0, 4, 3, 8]),
+            vec![0, 3, 4, 1, 5, 5, 1, 8]
+        );
+        assert_eq!(
+            phase(vec![0, 3, 4, 1, 5, 5, 1, 8]),
+            vec![0, 1, 0, 2, 9, 4, 9, 8]
+        );
+    }
+
+    #[test]
+    fn example2() {
+        let data: Vec<_> = "80871224585914546619083218645595"
+            .bytes()
+            .map(|i| (i - b'0') as i64)
+            .collect();
+        assert!(phase_n(data, 100)
+            .into_iter()
+            .take(8)
+            .eq(vec![2, 4, 1, 7, 6, 1, 7, 6]));
+    }
+
+    #[test]
+    fn example3() {
+        let data: Vec<_> = "19617804207202209144916044189917"
+            .bytes()
+            .map(|i| (i - b'0') as i64)
+            .collect();
+        assert!(phase_n(data, 100)
+            .into_iter()
+            .take(8)
+            .eq(vec![7, 3, 7, 4, 5, 4, 1, 8]));
+    }
+
+    #[test]
+    fn example4() {
+        let data: Vec<_> = "69317163492948606335995924319873"
+            .bytes()
+            .map(|i| (i - b'0') as i64)
+            .collect();
+        assert!(phase_n(data, 100)
+            .into_iter()
+            .take(8)
+            .eq(vec![5, 2, 4, 3, 2, 1, 3, 3]));
+    }
+}