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use pathfinding::prelude::yen;
// A simple tests of Yen's algorithm based on the example and visualization
// from https://en.wikipedia.org/wiki/Yen's_algorithm#Example.
#[test]
fn simple() {
let result = yen(
&'c',
|c| match c {
'c' => vec![('d', 3), ('e', 2)],
'd' => vec![('f', 4)],
'e' => vec![('d', 1), ('f', 2), ('g', 3)],
'f' => vec![('g', 2), ('h', 1)],
'g' => vec![('h', 2)],
'h' => vec![],
_ => panic!(""),
},
|c| *c == 'h',
3,
);
assert_eq!(result.len(), 3);
assert_eq!(result[0], (vec!['c', 'e', 'f', 'h'], 5));
assert_eq!(result[1], (vec!['c', 'e', 'g', 'h'], 7));
assert_eq!(result[2], (vec!['c', 'd', 'f', 'h'], 8));
}
/// Tests that we correctly return fewer routes when
/// we exhaust all possible paths.
#[test]
fn ask_more_than_exist() {
let result = yen(
&'c',
|c| match c {
'c' => vec![('d', 3), ('e', 2)],
'd' => vec![('f', 4)],
'e' => vec![('d', 1), ('f', 2), ('g', 3)],
'f' => vec![('g', 2), ('h', 1)],
'g' => vec![('h', 2)],
'h' => vec![],
_ => panic!(""),
},
|c| *c == 'h',
10,
);
// we asked for 10 but the graph can only produce 7
assert_eq!(
result.iter().map(|&(_, c)| c).collect::<Vec<_>>(),
vec![5, 7, 8, 8, 8, 11, 11]
);
}
/// Test that we return None in case there is no solution
#[test]
fn no_path() {
let result = yen(
&'c',
|c| match c {
'c' => vec![('d', 3), ('e', 2)],
'd' => vec![('f', 4)],
'e' => vec![('d', 1), ('f', 2), ('g', 3)],
'f' => vec![('g', 2), ('d', 1)],
'g' => vec![('e', 2)],
'h' => vec![],
_ => panic!(""),
},
|c| *c == 'h',
2,
);
assert!(result.is_empty());
}
/// Test that we support loops
#[test]
fn single_node() {
let result = yen(
&'c',
|c| match c {
'c' => vec![('c', 1)],
_ => panic!(""),
},
|c| *c == 'c',
2,
);
assert_eq!(result, vec![(vec!['c'], 0)]);
}
/// Test that we don't panic if an alternative path is more than two nodes longer than a previous one.
#[test]
fn longer_alternative_path() {
let result = yen(
&'c',
|c| match c {
'c' => vec![('d', 1), ('h', 1)],
'd' => vec![('e', 1)],
'e' => vec![('f', 1)],
'f' => vec![('g', 1), ('h', 1)],
'g' => vec![('h', 1)],
'h' => vec![],
_ => panic!(""),
},
|c| *c == 'h',
3,
);
assert_eq!(result.len(), 3);
assert_eq!(result[0], (vec!['c', 'h'], 1));
assert_eq!(result[1], (vec!['c', 'd', 'e', 'f', 'h'], 4));
assert_eq!(result[2], (vec!['c', 'd', 'e', 'f', 'g', 'h'], 5));
}
/// Check that we return all loopless paths
/// (issue #467)
#[test]
fn all_paths() {
let mut result = yen(
&'a',
|c| match c {
'a' => vec![('b', 1), ('c', 1), ('d', 1)],
'b' => vec![('c', 1), ('d', 1)],
'c' => vec![('b', 1), ('d', 1)],
'd' => vec![],
_ => unreachable!(),
},
|c| *c == 'd',
usize::MAX,
);
result.sort_unstable();
assert_eq!(
result,
vec![
(vec!['a', 'b', 'c', 'd'], 3),
(vec!['a', 'b', 'd'], 2),
(vec!['a', 'c', 'b', 'd'], 3),
(vec!['a', 'c', 'd'], 2),
(vec!['a', 'd'], 1),
]
);
}
#[test]
fn multiple_equal_cost_paths() {
use std::collections::HashMap;
// Graph example:
// A --> B --> D
// A --> C --> D
// Both paths (A -> B -> D) and (A -> C -> D) have the same cost of 2.
let mut graph = HashMap::new();
graph.insert('A', vec![('B', 1), ('C', 1)]);
graph.insert('B', vec![('D', 1)]);
graph.insert('C', vec![('D', 1)]);
graph.insert('D', vec![]); // Goal node
let successors = |n: &char| {
let neighbors = match n {
'A' => "BC",
'B' | 'C' => "D",
_ => "",
};
neighbors.chars().map(|n| (n, 1))
};
// Start is 'A', goal is 'D', and we want 2 shortest paths.
let paths = yen(&'A', successors, |n| *n == 'D', 2);
// We expect two distinct paths both with cost 2:
// Path 1: A -> B -> D
// Path 2: A -> C -> D
assert_eq!(paths.len(), 2);
// Check both paths have total cost of 2 and are distinct
assert_eq!(paths[0], (vec!['A', 'B', 'D'], 2));
assert_eq!(paths[1], (vec!['A', 'C', 'D'], 2));
}
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