78 lines
1.4 KiB
Rust
78 lines
1.4 KiB
Rust
use std::cmp::min;
|
|
|
|
#[derive(Debug)]
|
|
pub struct Graph {
|
|
pub n_nodes: usize,
|
|
pub n_edges: usize,
|
|
pub nodes: Vec<Node>,
|
|
}
|
|
|
|
#[derive(Debug)]
|
|
pub struct Node {
|
|
pub id: usize,
|
|
pub edges: Vec<Edge>,
|
|
}
|
|
|
|
#[derive(Debug)]
|
|
pub struct Edge {
|
|
pub source: usize,
|
|
pub target: usize,
|
|
pub length: i64,
|
|
}
|
|
|
|
pub fn floyd_warshall(g: Graph) -> Option<i64> {
|
|
let n = g.n_nodes;
|
|
let mut a: Vec<Vec<i64>> = vec![vec![std::i64::MAX; n]; n];
|
|
|
|
// nodes have lengths of 0 to themself
|
|
for i in 0..n {
|
|
a[i][i] = 0;
|
|
}
|
|
|
|
// nodes that are connected get the length of their edge
|
|
for n in &g.nodes {
|
|
for e in &n.edges {
|
|
a[e.source][e.target] = e.length;
|
|
}
|
|
}
|
|
|
|
// main workloop
|
|
for k in 0..n {
|
|
let mut new_a = a.to_vec();
|
|
for i in 0..n {
|
|
for j in 0..n {
|
|
let case_1 = a[i][j];
|
|
let case_2 = match a[i][k].checked_add(a[k][j]) {
|
|
Some(v) => v,
|
|
None => std::i64::MAX,
|
|
};
|
|
|
|
new_a[i][j] = min(case_1, case_2);
|
|
}
|
|
}
|
|
a = new_a;
|
|
}
|
|
|
|
// node to itself is negative means we have negative cost cycles
|
|
for i in 0..n {
|
|
if a[i][i] < 0 {
|
|
return None;
|
|
}
|
|
}
|
|
|
|
// find min path from v to u
|
|
let mut r = std::i64::MAX;
|
|
for i in 0..n {
|
|
for j in 0..n {
|
|
if i != j {
|
|
let d = a[i][j];
|
|
if d < r {
|
|
r = d;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
Some(r)
|
|
}
|