89 lines
2.3 KiB
Rust
89 lines
2.3 KiB
Rust
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//@ check-pass
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#![feature(adt_const_params, generic_const_exprs)]
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#![allow(incomplete_features)]
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mod lib {
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const N_ISLANDS: usize = 4;
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const N_BRIDGES: usize = 7;
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const BRIDGES: [(usize, usize); 7] = [(0, 1), (0, 1), (0, 2), (0, 3), (0, 3), (1, 2), (2, 3)];
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pub type Matrix = [[usize; N_ISLANDS]; N_ISLANDS];
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const EMPTY_MATRIX: Matrix = [[0; N_ISLANDS]; N_ISLANDS];
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const fn build(mut matrix: Matrix, (to, from): (usize, usize)) -> Matrix {
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matrix[to][from] += 1;
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matrix[from][to] += 1;
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matrix
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}
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pub const fn walk(mut matrix: Matrix, from: usize, to: usize) -> Matrix {
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matrix[from][to] -= 1;
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matrix[to][from] -= 1;
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matrix
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}
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const fn to_matrix(bridges: [(usize, usize); N_BRIDGES]) -> Matrix {
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let matrix = EMPTY_MATRIX;
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let matrix = build(matrix, bridges[0]);
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let matrix = build(matrix, bridges[1]);
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let matrix = build(matrix, bridges[2]);
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let matrix = build(matrix, bridges[3]);
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let matrix = build(matrix, bridges[4]);
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let matrix = build(matrix, bridges[5]);
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let matrix = build(matrix, bridges[6]);
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matrix
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}
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const BRIDGE_MATRIX: [[usize; N_ISLANDS]; N_ISLANDS] = to_matrix(BRIDGES);
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pub struct Walk<const CURRENT: usize, const REMAINING: Matrix> {
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_p: (),
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}
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impl Walk<0, BRIDGE_MATRIX> {
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pub const fn new() -> Self {
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Self { _p: () }
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}
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}
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impl<const CURRENT: usize, const REMAINING: Matrix> Walk<CURRENT, REMAINING> {
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pub fn proceed_to<const NEXT: usize>(
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self,
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) -> Walk<NEXT, { walk(REMAINING, CURRENT, NEXT) }> {
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Walk { _p: () }
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}
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}
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pub struct Trophy {
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_p: (),
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}
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impl<const CURRENT: usize> Walk<CURRENT, EMPTY_MATRIX> {
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pub fn collect_prize(self) -> Trophy {
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Trophy { _p: () }
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}
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}
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}
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pub use lib::{Trophy, Walk};
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fn main() {
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// Example, taking the first step
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let _ = Walk::new().proceed_to::<1>();
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// Don't be so eager to collect the trophy
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// let trophy = Walk::new()
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// .proceed_to::<1>()
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// .proceed_to::<0>()
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// .collect_prize();
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// Can't just make a Trophy out of thin air, you must earn it
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// let trophy: Trophy = Trophy { _p: () };
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// Can you collect the Trophy?
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}
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