Day 13 - task 2

src/days/d13.rs

@@ -6,6 +6,7 @@ pub fn solve() {
 
     let contents = fs::read_to_string(path).expect("I/O error, wrong path?");
 
+    // Task 1
     let pairs: Vec<(&str, &str)> = contents
         .split("\n\n")
         .map(|pair| pair.split_at(pair.find("\n").unwrap()))
@@ -16,10 +17,10 @@ pub fn solve() {
         let json1: Value = serde_json::from_str(pair.0).unwrap();
         let json2: Value = serde_json::from_str(pair.1).unwrap();
 
-        println!("== Pair {} ==", i+1);
+        // println!("== Pair {} ==", i+1);
         let res = is_right_order((&json1, &json2));
 
-        println!("Pair {}: {res:?}\n", i+1);
+        // println!("Pair {}: {res:?}\n", i+1);
 
         if res != Ordered::No {
             right_order_indices.push((i+1) as u32);
@@ -29,7 +30,46 @@ pub fn solve() {
     let res: u32 = right_order_indices.iter().sum();
     println!("Result 1: {res}");
 
+    // Task 2
+    let mut packets: Vec<Value> = contents
+        .lines()
+        .filter(|line| *line != "")
+        .map(|line| serde_json::from_str(line).unwrap())
+        .collect();
     
+    // add [[2]] and [[6]] as divider packets
+    packets.push(serde_json::from_str("[[6]]").unwrap());
+    packets.push(serde_json::from_str("[[2]]").unwrap());
+
+    // sort by compare function using is_right_order
+    packets.sort_by(|a, b| 
+        match is_right_order((a, b)) {
+            Ordered::Yes => Ordering::Less,
+            Ordered::Maybe => Ordering::Equal,
+            Ordered::No => Ordering::Greater
+    });
+
+    // find [[2]] and [[6]] indices
+    let mut i2 = 0;
+    let mut i6 = 0;
+    packets.iter().enumerate().for_each(|(i, v)| {
+        if v.is_array() && v.as_array().unwrap().len() == 1 {
+            let v = v.as_array().unwrap();
+            if v[0].is_array() && v[0].as_array().unwrap().len() == 1 {
+                let v = v[0].as_array().unwrap();
+                if v[0].is_number() && v[0].as_u64().unwrap() == 2 {
+                    i2 = i+1
+                }
+                else if v[0].is_number() && v[0].as_u64().unwrap() == 6 {
+                    i6 = i+1
+                }
+            }
+        }
+    });
+    
+    let res = i2*i6;
+
+    println!("Result 2: {res}");
 }
 
 #[derive(PartialEq, Debug)]
@@ -39,8 +79,10 @@ enum Ordered {
     No
 }
 
+// returns whether the passed Values are in the right order
+// with Ordered enum option
 fn is_right_order(values: (&Value, &Value)) -> Ordered {
-    println!("Compare {} vs {}", values.0, values.1);
+    //println!("Compare {} vs {}", values.0, values.1);
     
     // both values numbers
     if values.0.is_number() && values.1.is_number() {
@@ -79,14 +121,17 @@ fn is_right_order(values: (&Value, &Value)) -> Ordered {
             let left = a0iter.next();
             let right = a1iter.next();
 
+            // left smaller, counts as ordered
             if left.is_none() && right.is_some() {
                 return Ordered::Yes
             }
 
+            // right smaller, counts as unordered
             if left.is_some() && right.is_none() {
                 return Ordered::No
             }
 
+            // both have same length, doesn't say anything about ordering
             if left.is_none() && right.is_none() {
                 return Ordered::Maybe
             }
@@ -94,6 +139,7 @@ fn is_right_order(values: (&Value, &Value)) -> Ordered {
             let left = left.unwrap();
             let right = right.unwrap();
 
+            // only go into next iteration if not definitely yes or no
             let res = is_right_order((&left, &right));
             if res != Ordered::Maybe {
                 return res