puzzles 0.1.0

The library for solving puzzles like sliding puzzle.
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
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251

use crate::puzzle_sliding16::utils::{BITS_PER_CELL, BITS_PER_CELL_MASK64};
use std::iter::{FromIterator, FusedIterator};

/// Board state.
#[derive(Clone, Copy, PartialEq, Eq, Hash)]
pub struct State {
    /// Indexed by board indices, gives tiles numbers that occupy given board cell.
    pub board: u64,
    //board: [u8; MAX_BOARD_SIZE],

    // Index of blank (to speed up operations).
    //blank_position: u8
}

impl FromIterator<u8> for State {
    fn from_iter<T: IntoIterator<Item=u8>>(tiles: T) -> Self {
        let mut board = 0u64;
        let mut index = 0;
        for t in tiles {
            board |= (t as u64) << index;
            index += BITS_PER_CELL;
        }
        Self { board }
    }
}

/// Translate `tile` number from bottom-right format that assumes blank to be in the bottom-right corner of the goal state.
#[inline] pub fn from_bottom_right_format(tile: u8, board_size: u8) -> u8 {
    if tile == 0 { 0 } else {board_size-tile}
}

impl State {

    /// Constructs goal state for the board with board_size cells.
    pub fn goal(board_size: u8) -> Self {
        (0..board_size).collect()
    }

    /// Swap blank with the tile that occupy new_blank_position.
    /// Returns number of this tile.
    pub fn move_blank(&mut self, current_blank_position: u8, new_blank_position: u8) -> u8 {
        let new_blank_index = new_blank_position * BITS_PER_CELL;
        let result = (self.board >> new_blank_index) & BITS_PER_CELL_MASK64;
        self.board &= !(BITS_PER_CELL_MASK64 << new_blank_index);       // clear cell which should be blank
        self.board |= result << (current_blank_position * BITS_PER_CELL);    // set old blank cell to result
        result as u8
    }
    /*fn move_blank(&mut self, new_blank_position: u8) -> u8 {
        let new_blank_index = new_blank_position * BITS_PER_CELL;
        let result = (self.board >> new_blank_index) & BITS_PER_CELL_MASK64;
        self.board &= !(BITS_PER_CELL_MASK64 << new_blank_index);       // clear cell which should be blank
        self.board |= result << (self.blank_position*BITS_PER_CELL);    // set old blank cell to result
        self.blank_position = new_blank_position;
        result as u8
    }*/

    /// Constructs `State` from data given in format that assumes blank to be in the bottom-right corner of the goal state.
    pub fn from_bottom_right_format(tiles: &[u8]) -> Self {
        let s = tiles.len() as u8;
        tiles.iter().rev().map(|t| from_bottom_right_format(*t, s)).collect()
    }

    // Tile at position.
    pub fn tile_at(&self, position: u8) -> u8 {
        ((self.board >> (position * BITS_PER_CELL)) & BITS_PER_CELL_MASK64) as u8
    }

    /// Returns number of cells in board.
    pub fn board_size(&self) -> u8 {
        let mut c = self.board;
        let mut seen_blank = false;
        let mut result = 0;
        while c != 0 {
            result += 1;
            if (c & BITS_PER_CELL_MASK64) == 0 { seen_blank = true; }
            c >>= BITS_PER_CELL;
        }
        if !seen_blank { result += 1; }
        result
    }

    pub fn print(&self, cols: u8) {
        let mut to_print = self.board;
        let mut c = 0;
        loop {
            let cell = to_print & BITS_PER_CELL_MASK64;
            if cell==0 { print!(" "); } else { print!("{}", cell) };
            to_print >>= BITS_PER_CELL;
            if to_print == 0 {
                println!();
                break;
            }
            c += 1;
            if c == cols {
                println!();
                c = 0;
            } else { print!(" "); }
        }
    }

    #[inline] pub fn iter(&self) -> TilesIterator {
        TilesIterator::new(self.board)
    }
}

#[derive(Copy, Clone)]
pub struct TilesIterator {
    rest: u64,
    seen_blank: bool
}

impl TilesIterator {
    #[inline] pub fn new(board: u64) -> Self {
        Self { rest: board, seen_blank: false }
    }
}

impl Iterator for TilesIterator {
    type Item = u8;

    fn next(&mut self) -> Option<Self::Item> {
        if self.rest == 0 {
            if self.seen_blank {
                None
            } else {
                self.seen_blank = true;
                Some(0)
            }
        } else {
            let result = (self.rest & BITS_PER_CELL_MASK64) as u8;
            if result == 0 { self.seen_blank = true; }
            self.rest >>= BITS_PER_CELL;
            Some(result)
        }
    }
}

impl FusedIterator for TilesIterator {}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_from_and_move_blank_32() {
        let tiles = [2, 0, 5,  1, 4, 3];
        let mut state: State = tiles.iter().cloned().collect();
        assert_eq!(state.board_size(), 6);
        assert_eq!(state.tile_at(0), 2);
        assert_eq!(state.tile_at(1), 0);
        assert_eq!(state.tile_at(2), 5);
        assert_eq!(state.tile_at(3), 1);
        assert_eq!(state.tile_at(4), 4);
        assert_eq!(state.tile_at(5), 3);
        assert_eq!(state.iter().collect::<Vec<_>>(), &tiles);
        state.move_blank(1, 4);
        assert_eq!(state.board_size(), 6);
        assert_eq!(state.tile_at(0), 2);
        assert_eq!(state.tile_at(1), 4);    //<
        assert_eq!(state.tile_at(2), 5);
        assert_eq!(state.tile_at(3), 1);
        assert_eq!(state.tile_at(4), 0);    //<
        assert_eq!(state.tile_at(5), 3);
        assert_eq!(state.iter().collect::<Vec<_>>(), &[2, 4, 5, 1, 0, 3]);
        state.move_blank(4, 5);
        assert_eq!(state.board_size(), 6);
        assert_eq!(state.tile_at(0), 2);
        assert_eq!(state.tile_at(1), 4);
        assert_eq!(state.tile_at(2), 5);
        assert_eq!(state.tile_at(3), 1);
        assert_eq!(state.tile_at(4), 3);    //<
        assert_eq!(state.tile_at(5), 0);    //<
        assert_eq!(state.iter().collect::<Vec<_>>(), &[2, 4, 5, 1, 3, 0]);
    }

    #[test]
    fn test_from_and_move_blank_33() {
        let mut state: State = [4, 7, 0,   2, 3, 6,   8, 1, 5].iter().cloned().collect();
        assert_eq!(state.board_size(), 9);
        assert_eq!(state.tile_at(0), 4);
        assert_eq!(state.tile_at(1), 7);
        assert_eq!(state.tile_at(2), 0);
        assert_eq!(state.tile_at(3), 2);
        assert_eq!(state.tile_at(4), 3);
        assert_eq!(state.tile_at(5), 6);
        assert_eq!(state.tile_at(6), 8);
        assert_eq!(state.tile_at(7), 1);
        assert_eq!(state.tile_at(8), 5);
        state.move_blank(2, 5);
        assert_eq!(state.board_size(), 9);
        assert_eq!(state.tile_at(0), 4);
        assert_eq!(state.tile_at(1), 7);
        assert_eq!(state.tile_at(2), 6);    //<
        assert_eq!(state.tile_at(3), 2);
        assert_eq!(state.tile_at(4), 3);
        assert_eq!(state.tile_at(5), 0);    //<
        assert_eq!(state.tile_at(6), 8);
        assert_eq!(state.tile_at(7), 1);
        assert_eq!(state.tile_at(8), 5);
        state.move_blank(5, 4);
        assert_eq!(state.board_size(), 9);
        assert_eq!(state.tile_at(0), 4);
        assert_eq!(state.tile_at(1), 7);
        assert_eq!(state.tile_at(2), 6);
        assert_eq!(state.tile_at(3), 2);
        assert_eq!(state.tile_at(4), 0);    //<
        assert_eq!(state.tile_at(5), 3);    //<
        assert_eq!(state.tile_at(6), 8);
        assert_eq!(state.tile_at(7), 1);
        assert_eq!(state.tile_at(8), 5);
    }

    #[test]
    fn test_goal_33() {
        let state = State::goal(3*3);
        assert_eq!(state.board_size(), 9);
        assert_eq!(state.tile_at(0), 0);
        assert_eq!(state.tile_at(1), 1);
        assert_eq!(state.tile_at(2), 2);
        assert_eq!(state.tile_at(3), 3);
        assert_eq!(state.tile_at(4), 4);
        assert_eq!(state.tile_at(5), 5);
        assert_eq!(state.tile_at(6), 6);
        assert_eq!(state.tile_at(7), 7);
        assert_eq!(state.tile_at(8), 8);
    }

    #[test]
    fn test_goal_43() {
        let state = State::goal(4*3);
        assert_eq!(state.board_size(), 12);
        assert_eq!(state.tile_at(0), 0);
        assert_eq!(state.tile_at(1), 1);
        assert_eq!(state.tile_at(2), 2);
        assert_eq!(state.tile_at(3), 3);
        assert_eq!(state.tile_at(4), 4);
        assert_eq!(state.tile_at(5), 5);
        assert_eq!(state.tile_at(6), 6);
        assert_eq!(state.tile_at(7), 7);
        assert_eq!(state.tile_at(8), 8);
        assert_eq!(state.tile_at(9), 9);
        assert_eq!(state.tile_at(10), 10);
        assert_eq!(state.tile_at(11), 11);
    }

    #[test]
    fn test_from_bottom_right_format() {
        assert_eq!(from_bottom_right_format(0, 4), 0);
        assert_eq!(from_bottom_right_format(1, 4), 3);
    }
}