Add solution for 2020 day 04

2020/day-04/.gitignore

@@ -0,0 +1,2 @@
+part_one
+part_two

2020/day-04/common.rs

@@ -0,0 +1,30 @@
+use std::collections::HashMap;
+use std::fs::File;
+use std::io::{self, Read};
+use std::path::Path;
+
+pub type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;
+pub type Passport = HashMap<String, String>;
+
+pub fn read_file<P: AsRef<Path>>(path: P) -> io::Result<Vec<Passport>> {
+    let mut file = File::open(path)?;
+    let mut content = String::new();
+    file.read_to_string(&mut content)?;
+
+    let mut passports = vec![];
+
+    for passport in content.split("\n\n") {
+        let passport = passport.trim_end();
+        let pairs = passport.split(&['\n', ' ', ':'][..]).collect::<Vec<_>>();
+
+        let mut passport = Passport::new();
+
+        for pair in pairs.chunks_exact(2) {
+            passport.insert(pair[0].to_owned(), pair[1].to_owned());
+        }
+
+        passports.push(passport);
+    }
+
+    Ok(passports)
+}

2020/day-04/inputs/sample.txt

@@ -0,0 +1,13 @@
+ecl:gry pid:860033327 eyr:2020 hcl:#fffffd
+byr:1937 iyr:2017 cid:147 hgt:183cm
+
+iyr:2013 ecl:amb cid:350 eyr:2023 pid:028048884
+hcl:#cfa07d byr:1929
+
+hcl:#ae17e1 iyr:2013
+eyr:2024
+ecl:brn pid:760753108 byr:1931
+hgt:179cm
+
+hcl:#cfa07d eyr:2025 pid:166559648
+iyr:2011 ecl:brn hgt:59in

2020/day-04/part_one.rs

@@ -0,0 +1,29 @@
+mod common;
+
+use std::env;
+
+use common::{read_file, Passport, Result};
+
+fn check_valid(passports: Vec<Passport>) -> u64 {
+    let mut num_valid = 0;
+
+    for passport in passports {
+        if passport.len() == 8 || (passport.len() == 7 && !passport.contains_key("cid")) {
+            num_valid += 1;
+        }
+    }
+
+    num_valid
+}
+
+fn main() -> Result<()> {
+    let path = env::args().skip(1).next().unwrap();
+
+    let passports = read_file(path)?;
+
+    let num_valid = check_valid(passports);
+
+    println!("{}", num_valid);
+
+    Ok(())
+}

2020/day-04/part_two.rs

@@ -0,0 +1,74 @@
+mod common;
+
+use std::env;
+
+use common::{read_file, Passport, Result};
+
+fn check_valid(passports: Vec<Passport>) -> Result<u64> {
+    let mut num_valid = 0;
+
+    for passport in passports {
+        let mut valid =
+            passport.len() == 8 || (passport.len() == 7 && !passport.contains_key("cid"));
+
+        if !valid {
+            continue;
+        };
+
+        let birth_year = passport.get("byr").unwrap();
+        valid = valid
+            && birth_year.matches(|c: char| c.is_digit(10)).count() == 4
+            && (1920..=2002_u32).contains(&birth_year.parse()?);
+
+        let issue_year = passport.get("iyr").unwrap();
+        valid = valid
+            && issue_year.matches(|c: char| c.is_digit(10)).count() == 4
+            && (2010..=2020_u32).contains(&issue_year.parse()?);
+
+        let expir_year = passport.get("eyr").unwrap();
+        valid = valid
+            && expir_year.matches(|c: char| c.is_digit(10)).count() == 4
+            && (2020..=2030_u32).contains(&expir_year.parse()?);
+
+        let height = passport.get("hgt").unwrap();
+        let height_cm = height.strip_suffix("cm").map(|h| h.parse().unwrap());
+        let height_in = height.strip_suffix("in").map(|h| h.parse().unwrap());
+        valid = valid
+            && (height_cm.map(|h| (150..=193_u32).contains(&h)) == Some(true)
+                || height_in.map(|h| (59..=76_u32).contains(&h)) == Some(true));
+
+        let hair_color = passport.get("hcl").unwrap().strip_prefix("#");
+        valid = valid
+            && hair_color.is_some()
+            && hair_color
+                .unwrap()
+                .matches(|c: char| c.is_digit(16))
+                .count()
+                == 6;
+
+        let eye_color = passport.get("ecl").unwrap();
+        valid = valid
+            && ["amb", "blu", "brn", "gry", "grn", "hzl", "oth"].contains(&eye_color.as_str());
+
+        let pass_id = passport.get("pid").unwrap();
+        valid = valid && pass_id.matches(|c: char| c.is_digit(10)).count() == 9;
+
+        if valid {
+            num_valid += 1;
+        }
+    }
+
+    Ok(num_valid)
+}
+
+fn main() -> Result<()> {
+    let path = env::args().skip(1).next().unwrap();
+
+    let passports = read_file(path)?;
+
+    let num_valid = check_valid(passports)?;
+
+    println!("{}", num_valid);
+
+    Ok(())
+}

README.md

@@ -7,5 +7,5 @@
 -   [2017](2017/README.md) (0% completed)
 -   [2018](2018/README.md) (0% completed)
 -   [2019](2019/README.md) (0% completed)
--   [2020](2020/README.md) (12% completed)
+-   [2020](2020/README.md) (16% completed)
 -   [2021](2021/README.md) (16% completed)