day 15

day15/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day15"
+version = "0.1.0"

day15/Cargo.toml

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+[package]
+name = "day15"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day15/src/main.rs

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+use std::fs::read_to_string;
+use std::time::Instant;
+
+fn get_hash(data: &[u8]) -> u8 {
+    let mut state: u16 = 0;
+    for &c in data {
+        state += c as u16;
+        state *= 17;
+        state &= 255;
+    }
+    state as u8
+}
+
+fn main() {
+    let time_start = Instant::now();
+    let input_str = read_to_string("input.txt").unwrap();
+    let input_line = input_str.lines().next().unwrap();
+    let time_start_no_io = Instant::now();
+    // Task 1
+    let mut sum1: u32 = 0;
+    // Task 2
+    let mut sum2: u32 = 0;
+    // Rust is annoying
+    const NEW_VEC: Vec<(&[u8], u8)> = vec![];
+    let mut boxes: [Vec<(&[u8], u8)>; 256] = [NEW_VEC; 256];
+    // Processing the input
+    for str in input_line.split(',') {
+        let bytes = str.as_bytes();
+        // Task 1
+        sum1 += get_hash(bytes) as u32;
+        // Task 2
+        if *bytes.last().unwrap() == b'-' {
+            // Remove
+            let label = &bytes[..bytes.len()-1];
+            let hash = get_hash(label);
+            let target_box = &mut boxes[hash as usize];
+            if let Some(index) = target_box.iter().position(|(str, _)| *str == label ) {
+                target_box.remove(index);
+            }
+        } else {
+            // Insert / modify
+            let focal = bytes.last().unwrap() - b'0';
+            let label = &bytes[..bytes.len()-2];
+            let hash = get_hash(label);
+            let target_box = &mut boxes[hash as usize];
+            if let Some(index) = target_box.iter().position(|(str, _)| *str == label ) {
+                target_box[index] = (label, focal);
+            } else {
+                target_box.push((label, focal));
+            }
+        }
+    }
+    for (i, current_box) in boxes.iter().enumerate() {
+        let box_value = i + 1;
+        for (i, (_, focal)) in current_box.iter().enumerate() {
+            sum2 += (box_value * (i + 1) * *focal as usize) as u32;
+        }
+    }
+    let elapsed = time_start.elapsed().as_micros();
+    let elapsed_no_io = time_start_no_io.elapsed().as_micros();
+    println!("Time: {}us", elapsed);
+    println!("Time without file i/o: {}us", elapsed_no_io);
+    println!("Sum1: {}", sum1);
+    println!("Sum2: {}", sum2);
+}