day2 part1

src/02.rs

@@ -0,0 +1,74 @@
+use std::{fs::File, io::Read};
+use std::cmp;
+
+// instead of a map of player moves to the corresponding score, we just subtract the byte values
+// from our base value to get the score.
+const MY_CHOICE_ASCII_SCORE_BASE : char = 'W'; // character before X in ascii table
+const THEIR_CHOICE_ASCII_SCORE_BASE : char = '@'; // character before A in ascii table
+
+fn main() {
+    let filename = "input2.txt";
+    let file_result = File::open(filename);
+    let mut file = match file_result {
+        Ok(file)  => file,
+        Err(error)  => panic!("{}", error),
+    };
+    let mut contents = String::new();
+    match file.read_to_string(&mut contents) {
+        Ok(_) => {},
+        Err(error)  => panic!("{}", error),
+    }
+
+    let mut total_score :  u32 = 0;
+    for line in contents.lines() {
+        let me_char = line.chars().nth(2).unwrap();
+        let them_char = line.chars().nth(0).unwrap();
+
+
+        let their_move =  them_char as u8 - THEIR_CHOICE_ASCII_SCORE_BASE as u8;
+        let my_move =  me_char as u8 - MY_CHOICE_ASCII_SCORE_BASE as u8;
+
+
+        let round_score = fight_and_score(their_move, my_move);
+        total_score += round_score as u32 + my_move as u32;
+
+        println!("They:{} Me:{} Score:{}", get_human_readable(their_move), get_human_readable(my_move), round_score);
+
+    }
+
+    println!("Score: {}", total_score);
+}
+
+// Rock paper scissors. true means c1 won
+// ROCK = 0
+// PAPER = 1
+// SCISSORS = 2
+// mathy approach
+// If both numbers are the same, its a draw
+// If both numbers are consecutive, the bigger one wins
+// If both numbers aren’t consecutive, the smaller one wins
+//
+// returns the winning number
+fn fight_and_score(them: u8, me: u8) -> u8 {
+    let winner : u8 = match (me as i8  - them as i8).abs() {
+        0 => 100,
+        1 => cmp::max(me, them) ,
+        _ => cmp::min(me, them) ,
+    };
+
+    return match winner {
+        100 => 3, // draw is worth 3 points
+        w if w == me => 6,
+        w if w == them => 0,
+        _ => 255
+    };
+}
+
+fn get_human_readable(num: u8) -> char {
+    return match num {
+        1 => 'R',
+        2 => 'P',
+        3 => 'S',
+        _ => '!'
+    }
+}