Add day9 part2 - wip

Author: qselle

src/day9.rs

@@ -97,17 +97,92 @@ pub fn part1(input: &[Disk]) -> usize {
                     pos += 1;
                 }
             }
-            _ => unreachable!(),
+            Disk::Free { blocks } => {
+                for _ in 0..blocks {
+                    pos += 1;
+                }
+            }
         }
     }
     res
 }
 
-// #[aoc(day9, part2)]
-// pub fn part2(input: &[Disk]) -> usize {
-//     // dbg!(input);
-//     0
-// }
+#[aoc(day9, part2)]
+pub fn part2(input: &[Disk]) -> usize {
+    let mut i = 0;
+    let mut input = input.to_vec();
+
+    loop {
+        // for j in &input {
+        //     match j {
+        //         Disk::File { id, blocks } => {
+        //             print!("{}", id.to_string().repeat(*blocks));
+        //         }
+        //         Disk::Free { blocks } => {
+        //             print!("{}", ".".repeat(*blocks));
+        //         }
+        //     }
+        // }
+        // println!();
+
+        match input[i] {
+            Disk::File { id: _, blocks: _ } => {
+                i += 1;
+            }
+            Disk::Free {
+                blocks: free_blocks,
+            } => {
+                if let Some(last) = input.pop() {
+                    match last {
+                        Disk::Free { blocks: _ } => continue,
+                        Disk::File { id, blocks } => match blocks.cmp(&free_blocks) {
+                            std::cmp::Ordering::Equal => {
+                                input[i] = last;
+                                i += 1;
+                            }
+                            std::cmp::Ordering::Less => {
+                                input.insert(i, last);
+                                input[i + 1] = Disk::Free {
+                                    blocks: free_blocks - blocks,
+                                };
+                                i += 1;
+                            }
+                            std::cmp::Ordering::Greater => {
+                                input[i] = Disk::File {
+                                    id,
+                                    blocks: free_blocks,
+                                };
+                                input.push(Disk::File {
+                                    id,
+                                    blocks: blocks - free_blocks,
+                                });
+                                i += 1;
+                            }
+                        },
+                    }
+                }
+            }
+        }
+        if i >= input.len() {
+            break;
+        }
+    }
+
+    let mut res = 0;
+    let mut pos = 0;
+    for i in input {
+        match i {
+            Disk::File { id, blocks } => {
+                for _ in 0..blocks {
+                    res += pos * id;
+                    pos += 1;
+                }
+            }
+            _ => unreachable!(),
+        }
+    }
+    res
+}
 
 #[cfg(test)]
 mod tests {