Part 15

.vscode/launch.json

@@ -242,6 +242,24 @@
             },
             "args": [],
             "cwd": "${workspaceFolder}"
+        },
+        {
+            "type": "lldb",
+            "request": "launch",
+            "name": "Debug executable 'part15'",
+            "cargo": {
+                "args": [
+                    "build",
+                    "--bin=part15",
+                    "--package=advent-of-code-2023"
+                ],
+                "filter": {
+                    "name": "part15",
+                    "kind": "bin"
+                }
+            },
+            "args": [],
+            "cwd": "${workspaceFolder}"
         }
     ]
 }

src/bin/part15.rs

@@ -0,0 +1,120 @@
+use std::time;
+use std::collections::HashMap;
+
+#[derive(Debug, PartialEq, Eq, Hash)]
+struct Lens {
+    label: String,
+    focal_length: Option<u8>,
+}
+
+fn main() {
+    let t1 = time::Instant::now();
+
+    let data = load_input1();
+
+    let d1 = t1.elapsed();
+    println!("Loading: {:?}", d1);
+    let t2 = time::Instant::now();
+
+    let sum = data.iter().map(|d| *d as u32).sum::<u32>();
+
+    let d2 = t2.elapsed();
+    println!("Summing: {:?}", d2);
+    println!("Total: {:?}", d1 + d2);
+    println!("Sum: {}", sum);
+
+    let t3 = time::Instant::now();
+
+    let lenses = load_input2();
+    let mut boxes: HashMap<u8, Vec<Lens>> = HashMap::new();
+
+    for lens in lenses {
+        let box_id: u8 = hash(&lens.label);
+        
+        if lens.focal_length.is_none() { // - Operation
+            if let Some(relevant_box) = boxes.get_mut(&box_id) {
+                relevant_box.retain(|l| *l != lens);
+                if relevant_box.is_empty() {
+                    boxes.remove(&box_id);
+                }
+            }
+        } else { // = Operation
+            if let Some(relevant_box) = boxes.get_mut(&box_id) {
+                if let Some(relevant_lens) = relevant_box.iter_mut().find(|l| l.label == lens.label) {
+                    relevant_lens.focal_length = lens.focal_length;
+                } else {
+                    relevant_box.push(lens);
+                }
+            } else {
+                boxes.insert(box_id, vec![lens]);
+            }
+        }
+    }
+
+    let d3 = t3.elapsed();
+    println!("Hashing: {:?}", d3);
+    let t4 = time::Instant::now();
+
+    let mut total: u32 = 0;
+    for b in boxes {
+        for (i, l) in b.1.iter().enumerate() {
+            let mut product: u32 = 1 + b.0 as u32;
+            product *= 1 + i as u32;
+            product *= l.focal_length.unwrap() as u32;
+            total += product;
+        }
+    }
+
+    let d4 = t4.elapsed();
+    println!("Summing: {:?}", d4);
+    println!("Total: {:?}", d3 + d4);
+
+    println!("Result: {}", total);
+}
+
+fn hash(s: &str) -> u8 {
+    let mut h: u32 = 0;
+    for c in s.chars() {
+        h += c as u32;
+        h *= 17;
+        h = h % 256;
+    }
+    h as u8
+}
+
+fn load_input1() -> Vec<u8> {
+    let data = std::fs::read_to_string("src/bin/part15.txt")
+        .expect("Could not read file")
+        .split(',')
+        .map(|l| {
+            hash(l)
+        })
+        .collect::<Vec<_>>();
+
+    data
+}
+
+fn load_input2() -> Vec<Lens> {
+    let data: Vec<Lens> = std::fs::read_to_string("src/bin/part15.txt")
+        .expect("Could not read file")
+        .split(',')
+        .map(|l| {
+            if l.contains('-') {
+                return Lens{
+                    label: l.split('-').collect::<Vec<_>>()[0].to_string(),
+                    focal_length: None
+                }
+            } else if l.contains('=') {
+                let parts = l.split('=').collect::<Vec<_>>();
+                return Lens {
+                    label: parts[0].to_string(),
+                    focal_length: Some(parts[1].parse::<u8>().unwrap())
+                }
+            } else {
+                panic!("Invalid input");
+            }
+        })
+        .collect::<Vec<_>>();
+
+    data
+}

src/bin/part15.sample

@@ -0,0 +1 @@
+rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7