2016, 2017, 2018, 2024 puzzle progress

2024/src/bin/2024_09a.rs

@@ -0,0 +1,92 @@
+use core::read_data;
+
+fn display_filesystem(from: &[u32]) {
+    for (index, value) in from.iter().enumerate() {
+        if index.is_multiple_of(16) { println!(); }
+        if *value < u32::MAX { print!("{value}"); } else { print!("_"); }
+    }
+    println!();
+}
+
+fn build_filesystem(from: String) -> Vec<u32> {
+    let mut fs: Vec<u32> = vec![];
+    let mut file_entry = true;
+    let mut last_file_entry_id = 0;
+    for current_char in from.chars() {
+        let as_digit = current_char.to_digit(10).unwrap_or(0);
+
+        let (to_push, should_inc) = if file_entry {
+            (last_file_entry_id, true)
+        } else {
+            (u32::MAX, false)
+        };
+
+        if should_inc { last_file_entry_id += 1; }
+        for i in 0..as_digit {
+            fs.push(to_push)
+        }
+        file_entry = !file_entry;
+    }
+    fs
+}
+fn compact_filesystem(from: &[u32]) -> Vec<u32> {
+    let mut fs = from.clone().to_vec();
+
+    let mut left = 0;
+    let mut right = fs.len() - 1;
+    let fs_len = fs.len();
+
+    while left < right {
+        // find next empty slot from the left
+        while left < fs_len && fs[left] != u32::MAX {
+            left += 1;
+        }
+
+        // find next data slot from the right
+        while right > 0 && fs[right] == u32::MAX {
+            right -= 1;
+        }
+
+        if left >= right {
+            break;
+        }
+
+        // move data left
+        fs[left] = fs[right];
+        fs[right] = u32::MAX;
+    }
+
+    fs
+}
+
+fn calculate_checksum(from: &[u32]) -> u64 {
+    let mut checksum: u64 = 0;
+    for (index, &value) in from.iter().enumerate() {
+        if value != u32::MAX {
+            checksum += index as u64 * value as u64;
+        }
+    }
+    checksum
+}
+
+fn main() {
+    // let binding = "2333133121414131402".to_string();
+    let binding = read_data("2024_09_data.txt");
+    // build out the filesystem...
+    let mut filesystem = build_filesystem(binding);
+
+    println!("Filesystem built...");
+    // display_filesystem(&filesystem);
+    // ...start to compact it...
+
+    filesystem = compact_filesystem(&filesystem);
+
+    // ...calculate the checksum
+
+    // println!("filesystem post compact:");
+    // display_filesystem(&filesystem);
+    println!("Filesystem compacted...");
+    println!("Calculated Checksum = {} / Expected 1928", calculate_checksum(&filesystem));
+}
+
+// 6331212425418