From 4636c264b8547acfec3bf7cf0579537f1997cadc Mon Sep 17 00:00:00 2001
From: Martin Ashby <martin@ashbysoft.com>
Date: Sun, 25 Dec 2022 21:26:14 +0000
Subject: day25pt1

---
 input/day25.txt    | 100 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 input/day25_ex.txt |  13 +++++++
 src/day25.rs       |  73 ++++++++++++++++++++++++++++++++++++++
 src/main.rs        |   6 ++--
 4 files changed, 190 insertions(+), 2 deletions(-)
 create mode 100644 input/day25.txt
 create mode 100644 input/day25_ex.txt
 create mode 100644 src/day25.rs

diff --git a/input/day25.txt b/input/day25.txt
new file mode 100644
index 0000000..4118043
--- /dev/null
+++ b/input/day25.txt
@@ -0,0 +1,100 @@
+1=120=22222-=10-=
+1--22-=-
+21
+1=0222=-1=-0--220=02
+122102
+22--=20==2===201
+100-1-01=0-1
+20200-2==220120-
+2220-2200=000=
+1==002=221-2
+2--221-22=
+1022=121=1-22=-01
+2=1=1-1=02-=02=2=
+1-21112=02
+2=1-22021
+1---=-221=-22122
+10020
+1=--101
+1=12=02-1--12
+1=0-=1002020-2=
+120=1==201102==2==
+2==-=0120112=2-=-
+1---1
+12=2--02-00==-22
+12==1-=0-2=0--11--
+1=10=0-1221
+1=201-0-
+22
+10-0=21-2-1-2-=211
+1=1--12==0=--1
+2=-1022=1=-10-
+12-02-2-
+1=-1=00---
+1=100120=101
+112=01
+20-22=00-=1=1=10
+200--=0-221101=
+10-2=01=-20
+10=11=1
+20-1-
+2=012-002-02-1221
+1==1=1-012100
+10=221202-0-0-
+1-0121-
+2==1100-=
+102=022=202
+2=2-
+21-2=12-22-1
+1-2100
+1-200101==0
+2==0200-12012-=1=02
+1=1010-2=22=2
+1-2=-12-2-2=112=120
+1=-=-
+2-=
+100=0-1-1=000
+11=1-=2--00=0=2-=1
+1221120122=11110-
+111=10-002=
+20=-=200
+2==21
+1=--2=-=2-102211
+20=1=-0=1=
+12
+202=-0-=1220-0
+1=0112=1-=-1
+21-=-===0=-122000
+1=
+112010-11221=-00
+112-2==102=2-1=1
+1==-0=
+1=01-11-211
+21=-1-20--2=202122
+1=01
+20221
+100
+10=22-1=-1121-2
+2-0=-
+101012-200=010=
+1011=0011
+1-0202=0-11
+101==10
+10=
+10111-1=-0
+1112=0101=-
+11=0=-1111-000
+12=11
+1102222=20
+2=0=--==022-
+11222
+2100=
+1=-0
+12-11-2=-222-
+1-10-012=21-0
+1-2=
+112
+111=20
+1221=-2
+1===1==0010=0-
+1-=1-==-=20
\ No newline at end of file
diff --git a/input/day25_ex.txt b/input/day25_ex.txt
new file mode 100644
index 0000000..237ef0c
--- /dev/null
+++ b/input/day25_ex.txt
@@ -0,0 +1,13 @@
+1=-0-2
+12111
+2=0=
+21
+2=01
+111
+20012
+112
+1=-1=
+1-12
+12
+1=
+122
\ No newline at end of file
diff --git a/src/day25.rs b/src/day25.rs
new file mode 100644
index 0000000..2d26028
--- /dev/null
+++ b/src/day25.rs
@@ -0,0 +1,73 @@
+fn from_snafu(s: &str) -> i64 {
+    // This is the easy bit... 
+    let mut i: i64 = 0;
+    let mut pow: i64 = 1;
+    for ch in s.chars().rev() {
+        match ch {
+            '2' => i += 2 * pow,
+            '1' => i += 1 * pow,
+            '0' => {}, // additive identity!
+            '-' => i += -1 * pow,
+            '=' => i += -2 * pow,
+            _ => panic!("unexpected input {}", ch)
+        }
+        pow *= 5;
+    }
+    i
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_from_snafu() {
+        let cases = vec![
+        ("1=-0-2",     "1747"),
+        ( "12111",      "906"),
+        (  "2=0=",      "198"),
+        (    "21",       "11"), // works
+        (  "2=01",      "201"), // 201,1 > 40,0 > 8,= > 1,1
+        (   "111",       "31"), // works
+        ( "20012",     "1257"), //works
+        (   "112",       "32"), // works
+        ( "1=-1=",      "353"), // broke
+        (  "1-12",      "107"),
+        (    "12",        "7"),
+        (    "1=",        "3"),
+        (   "122",       "37"),
+        ];
+        for (snafu, decimal) in cases {
+            let x = from_snafu(snafu);
+            assert_eq!(x.to_string().as_str(), decimal);
+            assert_eq!(to_snafu(x), snafu);
+        }
+    }
+}
+
+fn to_snafu(mut i: i64) -> String {
+    // how to do this :thinking: add two, mod 5,take away 2? // nope
+    let mut res = Vec::<char>::new();
+    while i != 0 {
+        let d = ((i + 2) % 5) - 2;
+        let ch = match d {
+            2 => '2',
+            1 => '1',
+            0 => '0',
+            -1 => '-',
+            -2 => '=',
+            _ => panic!("unexpected digit {}", d)
+        };
+        res.push(ch);
+        i = (i + 2) / 5;
+    }
+    res.reverse();
+    res.into_iter().collect::<String>()
+    
+}
+
+pub fn run(input: String) {
+    let s: i64 = input.lines()
+        .map(from_snafu)
+        .sum();
+    println!("Day 25: {}", to_snafu(s));
+}
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index e865636..886b86c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -20,7 +20,8 @@ use std::fs;
 // mod day15;
 // mod day16;
 //mod day17;
-mod day18;
+//mod day18;
+mod day25;
 
 fn main() {
     // day1::run(fs::read_to_string("input/day1.txt").expect("Failed to read input file!"));
@@ -40,5 +41,6 @@ fn main() {
     // day15::run(fs::read_to_string("input/day15.txt").expect("Failed to read input file!"));
     // day16::run(fs::read_to_string("input/day16.txt").expect("Failed to read input file!"));
     //day17::run(fs::read_to_string("input/day17.txt").expect("Failed to read input file!"));
-    day18::run(fs::read_to_string("input/day18.txt").expect("Failed to read input file!"));
+    //day18::run(fs::read_to_string("input/day18.txt").expect("Failed to read input file!"));
+    day25::run(fs::read_to_string("input/day25.txt").expect("Failed to read input file!"));
 }
-- 
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