Rework day 1 solution to use one function for both parts

2017/day/1/src/main.rs

@@ -6,34 +6,19 @@ fn main() {
     let mut file = File::open("input").expect("unable to open input file");
     file.read_to_end(&mut input).expect("error reading input");
 
-    println!("{}", captcha(&input));
+    let digits = input.into_iter()
-    println!("{}", captcha2(&input));
+        .take_while(|&chr| chr >= 0x30 && chr <= 0x39)
-}
-
-fn captcha(input: &[u8]) -> u64 {
-    let digits = input.iter()
-        .take_while(|&&chr| chr >= 0x30 && chr <= 0x39)
         .collect::<Vec<_>>();
 
-    let mut sum = 0;
+    println!("{}", captcha(digits.as_slice(), 1));
-    for idx in 0..digits.len() {
+    println!("{}", captcha(digits.as_slice(), digits.len() / 2));
-        if digits[idx] == digits[(idx + 1) % digits.len()] {
-            sum += *digits[idx] as u64 - 0x30;
-        }
-    }
-
-    sum
 }
 
-fn captcha2(input: &[u8]) -> u64 {
+fn captcha(digits: &[u8], offset: usize) -> u64 {
-    let digits = input.iter()
-        .take_while(|&&chr| chr >= 0x30 && chr <= 0x39)
-        .collect::<Vec<_>>();
-
     let mut sum = 0;
     for idx in 0..digits.len() {
-        if digits[idx] == digits[(idx + (digits.len() / 2)) % digits.len()] {
+        if digits[idx] == digits[(idx + offset) % digits.len()] {
-            sum += *digits[idx] as u64 - 0x30;
+            sum += digits[idx] as u64 - 0x30;
         }
     }
 
@@ -44,54 +29,54 @@ fn captcha2(input: &[u8]) -> u64 {
 // third digit (2) matches the fourth digit.
 #[test]
 fn test_captcha_example1() {
-    assert_eq!(captcha(b"1122"), 3);
+    assert_eq!(captcha(b"1122", 1), 3);
 }
 
 // 1111 produces 4 because each digit (all 1) matches the next.
 #[test]
 fn test_captcha_example2() {
-    assert_eq!(captcha(b"1111"), 4);
+    assert_eq!(captcha(b"1111", 1), 4);
 }
 
 // 1234 produces 0 because no digit matches the next.
 #[test]
 fn test_captcha_example3() {
-    assert_eq!(captcha(b"1234"), 0);
+    assert_eq!(captcha(b"1234", 1), 0);
 }
 
 // 91212129 produces 9 because the only digit that matches the next one is the last digit, 9.
 #[test]
 fn test_captcha_example4() {
-    assert_eq!(captcha(b"91212129"), 9);
+    assert_eq!(captcha(b"91212129", 1), 9);
 }
 
 // 1212 produces 6: the list contains 4 items, and all four digits match the digit 2 items ahead.
 #[test]
 fn test_captcha2_example1() {
-    assert_eq!(captcha2(b"1212"), 6);
+    assert_eq!(captcha(b"1212", 2), 6);
 }
 
 // 1221 produces 0, because every comparison is between a 1 and a 2.
 #[test]
 fn test_captcha2_example2() {
-    assert_eq!(captcha2(b"1221"), 0);
+    assert_eq!(captcha(b"1221", 2), 0);
 }
 
 // 123425 produces 4, because both 2s match each other, but no other digit has a match.
 #[test]
 fn test_captcha2_example3() {
-    assert_eq!(captcha2(b"123425"), 4);
+    assert_eq!(captcha(b"123425", 3), 4);
 }
 
 // 123123 produces 12.
 #[test]
 fn test_captcha2_example4() {
-    assert_eq!(captcha2(b"123123"), 12);
+    assert_eq!(captcha(b"123123", 3), 12);
 }
 
 // 12131415 produces 4.
 #[test]
 fn test_captcha2_example5() {
-    assert_eq!(captcha2(b"12131415"), 4);
+    assert_eq!(captcha(b"12131415", 4), 4);
 }