d13p2

day13/src/main.rs

@@ -1,4 +1,5 @@
 use std::env;
+use std::cmp::Ordering;
 use std::fs::File;
 use std::io::{BufReader, BufRead};
 
@@ -17,40 +18,43 @@ fn parse_num(s: &[u8]) -> (u64, usize) {
 }
 
 // Assuming no malformed input
-fn is_in_order(left: &[u8], right: &[u8]) -> bool {
-    //println!(">> {:?}, {:?} -- {:?}", str::from_utf8(left), str::from_utf8(right));
+fn compare(left: &[u8], right: &[u8]) -> Ordering {
     if left.len() == 0 {
-        return true;
+        return Ordering::Less;
     }
     if right.len() == 0 {
-        return false;
+        return Ordering::Greater;
     }
     let (l, r) = (left[0], right[0]);
     if l == b',' && r == b',' {
-        is_in_order(&left[1..], &right[1..])
+        compare(&left[1..], &right[1..])
     } else if l == b'[' && r == b'[' {
-        is_in_order(&left[1..], &right[1..])
+        compare(&left[1..], &right[1..])
     } else if l == b']' && r == b']' {
-        is_in_order(&left[1..], &right[1..])
+        compare(&left[1..], &right[1..])
     } else if l == b']' {
-        true
+        Ordering::Less
     } else if r == b']' {
-        false
+        Ordering::Greater
     } else if l == b'[' {
         let (num, len) = parse_num(right);
-        is_in_order(&left, &[b"[", num.to_string().as_bytes(), b"]", &right[len..]].concat())
+        compare(
+            &left,
+            &[b"[", num.to_string().as_bytes(), b"]", &right[len..]].concat())
     } else if r == b'[' {
         let (num, len) = parse_num(left);
-        is_in_order(&[b"[", num.to_string().as_bytes(), b"]", &left[len..]].concat(), &right)
+        compare(
+            &[b"[", num.to_string().as_bytes(), b"]", &left[len..]].concat(),
+             &right)
     } else {
         let (lnum, llen) = parse_num(left);
         let (rnum, rlen) = parse_num(right);
         if lnum < rnum {
-            true
+            Ordering::Less
         } else if lnum > rnum {
-            false
+            Ordering::Greater
         } else {
-            is_in_order(&left[llen..], &right[rlen..])
+            compare(&left[llen..], &right[rlen..])
         }
     }
         
@@ -58,17 +62,20 @@ fn is_in_order(left: &[u8], right: &[u8]) -> bool {
 
 fn main() {
     let file = File::open(&env::args().nth(1).expect("input")).expect("io err");
-    let lines: Vec<String> = BufReader::new(file).lines().flatten().collect();
-    // TODO: array_chunks() for lazy iter?
-    let blocks: Vec<_> = lines.chunks(3).collect();
+    let mut lines: Vec<_> = BufReader::new(file).lines().flatten()
+        .filter(|line| line != "").collect();
+    lines.push(String::from("[[2]]"));
+    lines.push(String::from("[[6]]"));
+    lines.sort_unstable_by(|s1, s2| compare(s1.as_bytes(), s2.as_bytes()));
     
-    let mut sum = 0;
-    for (i, block) in blocks.iter().enumerate() {
-        // TODO: return error here instead of assert?
-        assert!((block.len() == 3 && block[2] == "") || block.len() == 2);
-        if is_in_order(block[0].as_bytes(), block[1].as_bytes()) {
-            sum += i + 1;
+    let (mut six, mut two): (usize, usize) = (0, 0);
+    for (i, line) in lines.iter().enumerate() {
+        if line == "[[6]]" {
+            six = i + 1;
+        }
+        if line == "[[2]]" {
+            two = i + 1;
         }
     }
-    println!("Answer: {:?}", sum);
+    println!("{:?}", six*two);
 }

day13/src/main1.rs

@@ -0,0 +1,74 @@
+use std::env;
+use std::fs::File;
+use std::io::{BufReader, BufRead};
+
+fn parse_num(s: &[u8]) -> (u64, usize) {
+    let mut num: u64 = 0;
+    let mut len = 0;
+    for i in 0..s.len() {
+        if s[i].is_ascii_digit() {
+            num = num*10 + (s[i] as u64 - '0' as u64);
+            len += 1;
+        } else {
+            break;
+        }
+    }
+    (num, len)
+}
+
+// Assuming no malformed input
+fn is_in_order(left: &[u8], right: &[u8]) -> bool {
+    //println!(">> {:?}, {:?} -- {:?}", str::from_utf8(left), str::from_utf8(right));
+    if left.len() == 0 {
+        return true;
+    }
+    if right.len() == 0 {
+        return false;
+    }
+    let (l, r) = (left[0], right[0]);
+    if l == b',' && r == b',' {
+        is_in_order(&left[1..], &right[1..])
+    } else if l == b'[' && r == b'[' {
+        is_in_order(&left[1..], &right[1..])
+    } else if l == b']' && r == b']' {
+        is_in_order(&left[1..], &right[1..])
+    } else if l == b']' {
+        true
+    } else if r == b']' {
+        false
+    } else if l == b'[' {
+        let (num, len) = parse_num(right);
+        is_in_order(&left, &[b"[", num.to_string().as_bytes(), b"]", &right[len..]].concat())
+    } else if r == b'[' {
+        let (num, len) = parse_num(left);
+        is_in_order(&[b"[", num.to_string().as_bytes(), b"]", &left[len..]].concat(), &right)
+    } else {
+        let (lnum, llen) = parse_num(left);
+        let (rnum, rlen) = parse_num(right);
+        if lnum < rnum {
+            true
+        } else if lnum > rnum {
+            false
+        } else {
+            is_in_order(&left[llen..], &right[rlen..])
+        }
+    }
+        
+}
+
+fn main() {
+    let file = File::open(&env::args().nth(1).expect("input")).expect("io err");
+    let lines: Vec<String> = BufReader::new(file).lines().flatten().collect();
+    // TODO: array_chunks() for lazy iter?
+    let blocks: Vec<_> = lines.chunks(3).collect();
+    
+    let mut sum = 0;
+    for (i, block) in blocks.iter().enumerate() {
+        // TODO: return error here instead of assert?
+        assert!((block.len() == 3 && block[2] == "") || block.len() == 2);
+        if is_in_order(block[0].as_bytes(), block[1].as_bytes()) {
+            sum += i + 1;
+        }
+    }
+    println!("Answer: {:?}", sum);
+}