1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135

use std::{collections::VecDeque, fmt::Display, str::Chars};

use advent_of_code::errors::Result;

use super::r#move::Move;

#[derive(Debug)]
pub struct Cargo {
    stacks: Vec<VecDeque<char>>,
}

fn read_cell(c: &mut Chars) -> Option<char> {
    c.next()?; // [
    let k = c.next()?; // cell
    c.next()?; // ]
    Some(k)
}

impl Cargo {
    pub fn from_lines<S: AsRef<str>, I: Iterator<Item = S>>(lines: &mut I) -> Result<Self> {
        let mut stacks = Vec::new();

        while let Some(line) = lines.next() {
            let line = line.as_ref();
            if line.is_empty() {
                break;
            }
            let mut index = 0;
            let mut chars = line.chars();
            while let Some(cell) = read_cell(&mut chars) {
                if stacks.len() <= index {
                    stacks.push(VecDeque::new());
                }
                if cell.is_alphabetic() {
                    stacks[index].push_front(cell)
                }
                // space between stacks
                if let None = chars.next() {
                    break;
                }
                index += 1;
            }
        }

        Ok(Cargo { stacks })
    }

    pub fn apply_move(&mut self, cargo_move: &Move) {
        if !cargo_move.is_valid(self.stacks.len()) {
            return;
        }
        let (from, to) = cargo_move.get_from_to_indices();
        let (from, to) = if from < to {
            let (from_slice, to_slice) = self.stacks.split_at_mut(to);
            let (_, from_slice) = from_slice.split_at_mut(from);
            (from_slice.first_mut(), to_slice.first_mut())
        } else {
            let (to_slice, from_slice) = self.stacks.split_at_mut(from);
            let (_, to_slice) = to_slice.split_at_mut(to);
            (from_slice.first_mut(), to_slice.first_mut())
        };
        if let (Some(from), Some(to)) = (from, to) {
            for _ in 0..cargo_move.amount() {
                if let Some(v) = from.pop_back() {
                    to.push_back(v);
                }
            }
        }
    }

    pub fn apply_move_keep_order(&mut self, cargo_move: &Move) {
        if !cargo_move.is_valid(self.stacks.len()) {
            return;
        }
        let (from, to) = cargo_move.get_from_to_indices();
        let (from, to) = if from < to {
            let (from_slice, to_slice) = self.stacks.split_at_mut(to);
            let (_, from_slice) = from_slice.split_at_mut(from);
            (from_slice.first_mut(), to_slice.first_mut())
        } else {
            let (to_slice, from_slice) = self.stacks.split_at_mut(from);
            let (_, to_slice) = to_slice.split_at_mut(to);
            (from_slice.first_mut(), to_slice.first_mut())
        };
        if let (Some(from), Some(to)) = (from, to) {
            let mut from_chars = VecDeque::with_capacity(cargo_move.amount());
            for _ in 0..cargo_move.amount() {
                if let Some(c) = from.pop_back() {
                    from_chars.push_front(c);
                }
            }
            to.extend(from_chars);
        }
    }

    pub fn get_tops(&self) -> String {
        let mut s = String::new();
        for stack in self.stacks.iter() {
            if let Some(c) = stack.get(stack.len() - 1) {
                s.push(*c);
            } else {
                s.push('#');
            }
        }
        s
    }
}

impl Display for Cargo {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let mut max_stack = 0;
        for stack in self.stacks.iter() {
            if stack.len() > max_stack {
                max_stack = stack.len();
            }
        }

        for i in (0..max_stack).rev() {
            for stack in self.stacks.iter() {
                if let Some(cell) = stack.get(i) {
                    write!(f, "[{}]", cell)?;
                } else {
                    write!(f, "   ")?;
                }
                write!(f, " ")?;
            }
            writeln!(f, "")?;
        }

        for i in 0..self.stacks.len() {
            write!(f, " {}  ", i + 1)?;
        }
        Ok(())
    }
}