Day 4 complete part 1 and 2

src/day4.rs

@@ -0,0 +1,64 @@
+use std::io;
+
+fn part1(x: &u32) -> bool {
+    let matching = x
+        .to_string()
+        .chars()
+        .map(|c| c.to_digit(10).unwrap())
+        .fold((true, false, 0), |acc, next| {
+            (acc.0 && next >= acc.2, acc.1 || next == acc.2, next)
+        });
+
+    matching.0 && matching.1
+}
+
+fn part2(x: &u32) -> bool {
+    let matching = x.to_string().chars().map(|c| c.to_digit(10).unwrap()).fold(
+        (true, false, 0, 0),
+        |acc, next| {
+            if next == acc.3 && acc.2 >= 2 {
+                (acc.0 && next >= acc.3, acc.1, acc.2 + 1, next)
+            } else if next != acc.3 && acc.2 == 2 {
+                (acc.0 && next >= acc.3, true, 1, next)
+            } else if next == acc.3 && acc.2 < 2 {
+                (acc.0 && next >= acc.3, acc.1, acc.2 + 1, next)
+            } else {
+                (acc.0 && next >= acc.3, acc.1, 1, next)
+            }
+        },
+    );
+    matching.0 && (matching.1 || matching.2 == 2)
+}
+
+pub fn main() -> io::Result<()> {
+    let input = "123257-647015";
+
+    let range: Vec<u32> = input
+        .split("-")
+        .map(|x| x.parse::<u32>().unwrap())
+        .take(2)
+        .collect();
+
+    println!("part1 = {}", (range[0]..range[1]).filter(part1).count());
+    println!("part2 = {}", (range[0]..range[1]).filter(part2).count());
+
+    Ok(())
+}
+
+#[test]
+fn test_part1() {
+    assert!(part1(&111111));
+    assert!(!part1(&223450));
+    assert!(!part1(&123789));
+}
+
+#[test]
+fn test_part2() {
+    assert!(!part2(&111111));
+    assert!(!part2(&223450));
+    assert!(!part2(&123789));
+    assert!(part2(&112233));
+    assert!(part2(&223334));
+    assert!(!part2(&123444));
+    assert!(part2(&111122));
+}

src/main.rs

@@ -1,6 +1,7 @@
 mod day1;
 mod day2;
 mod day3;
+mod day4;
 
 use std::fs::File;
 use std::io::{self, BufRead, BufReader};
@@ -18,5 +19,7 @@ fn main() -> io::Result<()> {
 
     day3::main()?;
 
+    day4::main()?;
+
     Ok(())
 }