bitsets for fast checking if a number fits (slower)
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3841F1C27E6F0E14
215
src/main.rs
215
src/main.rs
@ -1,33 +1,80 @@
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use std::time::Instant;
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const MAX_BLOCK_SIZE: usize = 10;
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#[derive(Copy, Clone, Debug)]
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struct Bitset {
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set: u16,
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}
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impl Bitset {
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pub fn new() -> Self {
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Self { set: 0 }
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}
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#[inline(always)]
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fn get(&self, nr: usize) -> bool {
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self.set & (1 << nr) != 0
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}
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#[inline(always)]
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fn set(&mut self, nr: usize) {
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self.set |= 1 << nr;
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}
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#[inline(always)]
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fn unset(&mut self, nr: usize) {
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self.set &= !(1 << nr);
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}
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}
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const BLOCK_SIZE: usize = 4;
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//const MAX_BLOCK_SIZE: usize = 10;
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struct SField {
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field: Vec<usize>,
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fixed: Vec<usize>,
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size: usize,
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block_size: usize,
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pos: usize,
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pos_last_placed: usize,
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num_fields: usize,
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possible_values: Vec<Vec<usize>>,
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// For each row/col/block we create a bitset that represents the numbers
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// that are already in that row, col or block.
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// This way we can check very fast if a nr fits into a specific field or not.
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rows: [Bitset; BLOCK_SIZE * BLOCK_SIZE],
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cols: [Bitset; BLOCK_SIZE * BLOCK_SIZE],
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blocks: [Bitset; BLOCK_SIZE * BLOCK_SIZE],
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}
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#[inline(always)]
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fn xy_to_pos(x: usize, y: usize, size: usize) -> usize {
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y * size + x
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}
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#[inline(always)]
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fn pos_to_xy_blocknr(pos: usize, size: usize) -> (usize, usize, usize) {
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let x = pos % size;
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let y = pos / size;
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let block_x = x / BLOCK_SIZE;
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let block_y = y / BLOCK_SIZE;
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let block_nr = block_y * BLOCK_SIZE + block_x;
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(x, y, block_nr)
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}
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impl SField {
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pub fn new(block_size: usize) -> SField {
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if block_size > MAX_BLOCK_SIZE {
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panic!("block size cannot be larger than {}", MAX_BLOCK_SIZE);
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}
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let size = block_size * block_size;
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pub fn new() -> SField {
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const SIZE: usize = BLOCK_SIZE * BLOCK_SIZE;
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// EMPTY FIELD
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// let field = vec![0; size * size];
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// BLOCK_SIZE 4
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#[rustfmt::skip]
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let field = vec![
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0,15,0,0,0,0,11,4,0,5,0,0,0,0,12,8,
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let field = match BLOCK_SIZE {
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4 => vec![
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0usize,15,0,0,0,0,11,4,0,5,0,0,0,0,12,8,
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12,0,0,9,0,1,0,5,0,0,8,15,0,0,0,13,
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0,0,3,0,0,10,13,0,0,11,4,0,15,0,6,0,
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13,10,0,11,0,0,0,14,0,3,2,0,0,9,0,0,
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@ -43,7 +90,20 @@ impl SField {
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0,3,0,14,0,0,9,6,0,0,0,0,0,4,0,0,
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0,4,6,0,0,7,0,0,0,0,0,0,0,0,0,0,
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5,2,0,0,0,4,10,15,1,0,3,0,0,0,7,0,
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];
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],
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3 => vec![
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0,0,0,0,0,0,0,0,9,
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0,0,0,0,8,9,0,2,0,
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0,0,0,0,2,0,4,0,0,
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0,0,4,0,6,0,0,0,8,
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0,0,0,5,0,0,0,0,0,
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0,6,5,0,0,2,0,7,4,
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0,3,0,0,0,5,0,4,0,
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0,0,1,8,0,0,0,0,0,
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0,0,8,2,0,0,0,6,0,
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],
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_ => panic!("Unsupported block size. Only 3 and 4 is ok for now.")
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};
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// MANY SOLUTIONS
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// #[rustfmt::skip]
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@ -87,7 +147,7 @@ impl SField {
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// 7,3,6,0,2,0,0,0,0,
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// ];
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let mut fixed = Vec::with_capacity(size * size);
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let mut fixed = Vec::with_capacity(SIZE * SIZE);
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field.iter().for_each(|e| {
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if *e == 0 {
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fixed.push(0);
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@ -96,15 +156,82 @@ impl SField {
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}
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});
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// create bitsets
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// rows
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let mut bit_rows = [Bitset::new(); SIZE];
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for row_nr in 0..SIZE {
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let mut row = [0; SIZE];
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for count in 0..SIZE {
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row[count] = field[xy_to_pos(count, row_nr, SIZE)];
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}
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row.into_iter()
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.filter(|val| *val != 0)
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.for_each(|val| bit_rows[row_nr].set(val - 1));
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}
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// cols
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let mut bit_cols = [Bitset::new(); SIZE];
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for col_nr in 0..SIZE {
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let mut col = [0; SIZE];
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for count in 0..SIZE {
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col[count] = field[xy_to_pos(col_nr, count, SIZE)];
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}
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col.into_iter()
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.filter(|val| *val != 0)
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.for_each(|val| bit_cols[col_nr].set(val - 1));
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}
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// blocks
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let mut bit_blocks = [Bitset::new(); SIZE];
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for block_nr in 0..SIZE {
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let block_start_x = block_nr * BLOCK_SIZE % SIZE;
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let block_start_y = block_nr * BLOCK_SIZE / SIZE * BLOCK_SIZE;
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let mut block = [0; SIZE];
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for count in 0..SIZE {
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let block_offset_x = count % BLOCK_SIZE;
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let block_offset_y = count / BLOCK_SIZE;
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let field_x = block_start_x + block_offset_x;
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let field_y = block_start_y + block_offset_y;
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//dbg!(
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//block_nr,
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//block_start_x,
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//block_start_y,
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//block_offset_x,
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//block_offset_y,
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//field_x,
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//field_y,
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//);
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block[count] = field[xy_to_pos(field_x, field_y, SIZE)];
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}
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block
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.into_iter()
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.filter(|x| *x != 0)
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.for_each(|x| bit_blocks[block_nr].set(x - 1));
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}
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//dbg!(bit_rows);
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//dbg!(bit_cols);
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//dbg!(bit_blocks);
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SField {
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field,
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fixed,
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size,
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block_size,
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size: SIZE,
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pos: 0,
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pos_last_placed: 0,
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num_fields: size * size,
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possible_values: vec![vec![]; size * size],
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num_fields: SIZE * SIZE,
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possible_values: vec![vec![]; SIZE * SIZE],
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rows: bit_rows,
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cols: bit_cols,
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blocks: bit_blocks,
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}
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}
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@ -148,11 +275,11 @@ impl SField {
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if self.is_end() {
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found_solution = true;
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num_solutions += 1;
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if num_solutions % 100 == 0 {
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self.print_clear();
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println!("Solutions: {}", num_solutions);
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self.print();
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}
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//if num_solutions % 100 == 0 {
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//self.print_clear();
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//println!("Solutions: {}", num_solutions);
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//self.print();
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//}
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if self.is_fixed() {
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continue;
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@ -296,8 +423,9 @@ impl SField {
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continue;
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}
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if self.ok(*nr) {
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self.set(*nr);
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let nr = *nr;
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if self.ok(nr) {
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self.set(nr);
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return true;
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}
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}
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@ -311,14 +439,11 @@ impl SField {
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#[inline(always)]
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fn ok(&self, nr: usize) -> bool {
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self.block_ok(nr) && self.row_ok(nr) && self.col_ok(nr)
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}
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//self.block_ok(nr) && self.row_ok(nr) && self.col_ok(nr)
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#[inline(always)]
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fn _pos_to_xy(&self) -> (usize, usize) {
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let y = self.pos / self.size;
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let x = self.pos % self.size;
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(x + 1, y + 1)
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let (x, y, block_nr) = pos_to_xy_blocknr(self.pos, self.size);
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!self.rows[y].get(nr - 1) && !self.cols[x].get(nr - 1) && !self.blocks[block_nr].get(nr - 1)
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}
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#[inline(always)]
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@ -340,10 +465,32 @@ impl SField {
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#[inline(always)]
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fn set(&mut self, nr: usize) {
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self.field[self.pos] = nr;
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let old = unsafe { self.field.get_unchecked_mut(self.pos) };
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// if another number > 0 was in that cell, we need to remove that number from our bitsets
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if *old > 0 {
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let (x, y, block_nr) = pos_to_xy_blocknr(self.pos, self.size);
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self.rows[y].unset(*old - 1);
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self.cols[x].unset(*old - 1);
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self.blocks[block_nr].unset(*old - 1);
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}
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// add new nr to our bitsets if it is a meaningful (> 0) number
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if nr > 0 {
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let (x, y, block_nr) = pos_to_xy_blocknr(self.pos, self.size);
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self.rows[y].set(nr - 1);
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self.cols[x].set(nr - 1);
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self.blocks[block_nr].set(nr - 1);
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}
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// write the new number into the field
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*old = nr;
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// remember the last placed position for debugging purposes
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self.pos_last_placed = self.pos;
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}
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/*
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#[inline(always)]
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fn get_row(&self, row: &mut [usize]) {
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for (idx, row_elem) in row.iter_mut().enumerate() {
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@ -391,6 +538,7 @@ impl SField {
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self.get_col(&mut col[0..self.size]);
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!col.contains(&nr)
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}
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*/
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#[inline(always)]
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fn next(&mut self) -> bool {
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@ -398,6 +546,7 @@ impl SField {
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return false;
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}
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//println!("next {} -> {}", self.pos, self.pos + 1);
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self.pos += 1;
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true
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}
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@ -423,7 +572,7 @@ impl SField {
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}
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fn run() -> Result<(), String> {
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let mut field = SField::new(4);
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let mut field = SField::new();
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field.build_possible_values_db();
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