52 lines
1.5 KiB
Rust
52 lines
1.5 KiB
Rust
//! xkcd Knapsack Problem.
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//!
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//! https://en.wikipedia.org/wiki/Knapsack_problem
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//! https://xkcd.com/287/
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extern crate num_rational;
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extern crate num_traits;
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extern crate puzzle_solver;
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use num_rational::Ratio;
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use num_traits::ToPrimitive;
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use puzzle_solver::{LinExpr,Puzzle,Val};
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#[test]
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fn xkcd_knapsack() {
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let menu = [
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(Ratio::new(2_15, 100), "Mixed Fruit"),
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(Ratio::new(2_75, 100), "French Fries"),
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(Ratio::new(3_35, 100), "Side Salad"),
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(Ratio::new(3_55, 100), "Hot Wings"),
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(Ratio::new(4_20, 100), "Mozzarella Sticks"),
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(Ratio::new(5_80, 100), "Sampler Plate"),
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];
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let mut sys = Puzzle::new();
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let mut vars = Vec::with_capacity(menu.len());
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let total = Ratio::new(15_05, 100);
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for &(cost, _) in menu.iter() {
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let num = (total / cost).floor().to_integer();
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let var = sys.new_var_with_candidates(&(0..(num + 1)).collect::<Vec<Val>>());
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vars.push(var)
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}
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sys.equals(total, vars.iter().zip(menu.iter()).fold(LinExpr::from(0),
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|sum, (&var, &(cost, _))| sum + var * cost));
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let solutions = sys.solve_all();
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assert_eq!(solutions.len(), 2);
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for dict in solutions.iter() {
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println!("");
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for (&var, &(cost, string)) in vars.iter().zip(menu.iter()) {
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let numer = cost.numer().to_f32().unwrap();
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let denom = cost.denom().to_f32().unwrap();
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println!(" {} x {:.2} {}", dict[var], numer / denom, string);
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}
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}
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println!("xkcd_knapsack: {} guesses", sys.num_guesses());
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}
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