From 6dab82d7ebd2edea2a1220cfbaff977528c6aaca Mon Sep 17 00:00:00 2001
From: cos <cos>
Date: Sat, 5 Dec 2020 00:34:36 +0100
Subject: Refactor day04 to make full use of regex

---
 2020/rust/day04/src/main.rs | 95 ++++++++++++---------------------------------
 1 file changed, 25 insertions(+), 70 deletions(-)

(limited to '2020')

diff --git a/2020/rust/day04/src/main.rs b/2020/rust/day04/src/main.rs
index 34ae9bc..0d4c901 100644
--- a/2020/rust/day04/src/main.rs
+++ b/2020/rust/day04/src/main.rs
@@ -50,81 +50,36 @@ fn part1(input: &[Passport]) -> usize {
 
 fn part2(input: &[Passport]) -> Result<usize> {
     let mut valid_count = 0;
-    let hgt_re = Regex::new(r"^(?P<value>\d+)(?P<unit>cm|in)$")?;
-    let hcl_re = Regex::new(r"^#[0-9a-f]{6}$")?;
-    let ecl_re = Regex::new(r"^(amb|blu|brn|gry|grn|hzl|oth)$")?;
-    let pid_re = Regex::new(r"^\d{9}$")?;
+    let mut re: HashMap<String, Regex> = HashMap::new();
+
+    // byr (Birth Year) - four digits; at least 1920 and at most 2002.
+    re.insert(String::from("byr"), Regex::new(r"^(19[2-9][0-9])|(200[0-2])$")?);
+    // iyr (Issue Year) - four digits; at least 2010 and at most 2020.
+    re.insert(String::from("iyr"), Regex::new(r"^20(1[0-9])|(20)$")?);
+    // eyr (Expiration Year) - four digits; at least 2020 and at most 2030.
+    re.insert(String::from("eyr"), Regex::new(r"^20(2[0-9])|(30)$")?);
+    // hgt (Height) - a number followed by either cm or in:
+    // If cm, the number must be at least 150 and at most 193.
+    // If in, the number must be at least 59 and at most 76.
+    re.insert(String::from("hgt"),
+        Regex::new(r"^1(([5-8][0-9])|(9[0-3]))cm|((59)|(6[0-9])|(7[0-6]))in$")?);
+    // hcl (Hair Color) - a # followed by exactly six characters 0-9 or a-f.
+    re.insert(String::from("hcl"), Regex::new(r"^#[0-9a-f]{6}$")?);
+    // ecl (Eye Color) - exactly one of: amb blu brn gry grn hzl oth.
+    re.insert(String::from("ecl"), Regex::new(r"^(amb|blu|brn|gry|grn|hzl|oth)$")?);
+    // pid (Passport ID) - a nine-digit number, including leading zeroes.
+    re.insert(String::from("pid"), Regex::new(r"^\d{9}$")?);
+    // cid (Country ID) - ignored, missing or not.
 
     'validate: for passport in input {
-        // byr (Birth Year) - four digits; at least 1920 and at most 2002.
-        match passport.get("byr") {
-            Some(byr) => match byr.parse() {
-                Ok(1920..=2002) => {},
-                _ => continue 'validate,
-            }
-            _ => continue 'validate,
-        }
-        // iyr (Issue Year) - four digits; at least 2010 and at most 2020.
-        match passport.get("iyr") {
-            Some(iyr) => match iyr.parse() {
-                Ok(2010..=2020) => {},
-                _ => continue 'validate,
-            }
-            _ => continue 'validate,
-        }
-        // eyr (Expiration Year) - four digits; at least 2020 and at most 2030.
-        match passport.get("eyr") {
-            Some(eyr) => match eyr.parse() {
-                Ok(2020..=2030) => {},
+        for key in &["byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"] {
+            match (passport.get(*key), re.get(*key)) {
+                (Some(val), Some(re)) => if ! re.is_match(val) {
+                    continue 'validate;
+                },
                 _ => continue 'validate,
             }
-            _ => continue 'validate,
-        }
-        // hgt (Height) - a number followed by either cm or in:
-        // If cm, the number must be at least 150 and at most 193.
-        // If in, the number must be at least 59 and at most 76.
-        match passport.get("hgt") {
-            Some(hgt) => match hgt_re.captures(hgt) {
-                    Some(caps) => match &caps.name("unit") {
-                        Some(unit) => match unit.as_str() {
-                            "cm" => match &caps.name("value") {
-                                Some(value) => match value.as_str().parse() {
-                                    Ok(150..=193) => {},
-                                _ => continue 'validate,
-                                }
-                                _ => continue 'validate,
-                            },
-                            "in" => match &caps.name("value") {
-                                Some(value) => match value.as_str().parse() {
-                                    Ok(59..=76) => {},
-                                    _ => continue 'validate,
-                                },
-                                _ => continue 'validate,
-                            },
-                            _ => continue 'validate,
-                        }
-                        None => continue 'validate,
-                    }
-                    None => continue 'validate,
-                }
-            _ => continue 'validate,
-        }
-        // hcl (Hair Color) - a # followed by exactly six characters 0-9 or a-f.
-        match passport.get("hcl") {
-            Some(hcl) if hcl_re.is_match(hcl) => {},
-            _ => continue 'validate,
-        }
-        // ecl (Eye Color) - exactly one of: amb blu brn gry grn hzl oth.
-        match passport.get("ecl") {
-            Some(ecl) if ecl_re.is_match(ecl) => {},
-            _ => continue 'validate,
-        }
-        // pid (Passport ID) - a nine-digit number, including leading zeroes.
-        match passport.get("pid") {
-            Some(pid) if pid_re.is_match(pid) => {},
-            _ => continue 'validate,
         }
-        // cid (Country ID) - ignored, missing or not.
         valid_count += 1;
     }
 
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