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asd-2024
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Antonio De Lucreziis 3 weeks ago
parent e3b5d1f7da
commit 509f0a54e8
3 changed files with 100 additions and 88 deletions
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5
examples/edge_classify.py
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@ -1,6 +1,7 @@
# code
import random
# Algorithm from GeeksforGeeks (wrong)
# https://www.geeksforgeeks.org/tree-back-edge-and-cross-edges-in-dfs-of-graph/
import random
class Graph:
# instance variables

3
examples/edge_classify_2.py
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@ -1,3 +1,6 @@
# Algorithm from MIT OpenCourseWare (seems correct)
# https://courses.csail.mit.edu/6.006/fall11/rec/rec14.pdf
class DFSResult:
def __init__(self):
self.parent = {}

180
src/graph/edge_types.rs
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@ -22,93 +22,101 @@ where
V: Hash + Eq + Clone + Debug,
{
pub fn compute_edge_types(&self) -> HashMap<(&V, &V), EdgeType> {
/// To correctly compute the start and end times of the nodes in the
/// graph, we need to keep do work before and after the recursion call
enum RecurseState<'a, V> {
Before(&'a V),
BeforeNeighbor(&'a V, &'a V),
AfterNeighbor(&'a V),
}
let mut edge_types = HashMap::new();
let mut visited = HashSet::new();
let mut start_times = HashMap::new();
let mut finished_nodes = HashSet::new();
let mut time = 0;
let progress_bar = ProgressBar::new(self.nodes().len() as u64);
for node in self.nodes().iter() {
if visited.contains(node) {
continue;
}
let mut stack = Vec::new();
stack.push(RecurseState::Before(node));
while let Some(state) = stack.pop() {
match state {
RecurseState::Before(node) => {
progress_bar.inc(1);
visited.insert(node.clone());
start_times.insert(node, time);
time += 1;
// this is extremely important that is before the adjacencies to correctly
// iterate over the graph
if let Some(adjacencies) = self.get_adjacencies(node) {
for adj in adjacencies {
println!("Node: {:?} Adj: {:?}", node, adj,);
stack.push(RecurseState::AfterNeighbor(node));
if !visited.contains(adj) {
edge_types.insert((node, adj), EdgeType::TreeEdge);
stack.push(RecurseState::Before(adj));
} else {
stack.push(RecurseState::BeforeNeighbor(node, adj));
}
}
}
}
RecurseState::AfterNeighbor(node) => {
finished_nodes.insert(node, time);
time += 1;
}
RecurseState::BeforeNeighbor(node, adj) => {
let start_time_node = start_times.get(node).unwrap();
let start_time_adj = start_times.get(adj).unwrap();
let end_time_node = finished_nodes.get(node).unwrap_or(&0);
let end_time_adj = finished_nodes.get(adj).unwrap_or(&0);
println!(
"Times: ({:?}, {:?}) ({:?}, {:?})",
start_time_node, end_time_node, start_time_adj, end_time_adj
);
match (
start_time_node.cmp(start_time_adj),
end_time_node.cmp(end_time_adj),
) {
(Ordering::Less, Ordering::Greater) => {
edge_types.insert((node, adj), EdgeType::ForwardEdge);
}
(Ordering::Greater, Ordering::Less) => {
edge_types.insert((node, adj), EdgeType::BackEdge);
}
_ => {
edge_types.insert((node, adj), EdgeType::CrossEdge);
}
}
}
}
}
}
edge_types
// TODO: ...
return edge_types;
}
// pub fn compute_edge_types(&self) -> HashMap<(&V, &V), EdgeType> {
// /// To correctly compute the start and end times of the nodes in the
// /// graph, we need to keep do work before and after the recursion call
// enum RecurseState<'a, V> {
// Before(&'a V),
// BeforeNeighbor(&'a V, &'a V),
// AfterNeighbor(&'a V),
// }
// let mut edge_types = HashMap::new();
// let mut visited = HashSet::new();
// let mut start_times = HashMap::new();
// let mut finished_nodes = HashSet::new();
// let mut time = 0;
// let progress_bar = ProgressBar::new(self.nodes().len() as u64);
// for node in self.nodes().iter() {
// if visited.contains(node) {
// continue;
// }
// let mut stack = Vec::new();
// stack.push(RecurseState::Before(node));
// while let Some(state) = stack.pop() {
// match state {
// RecurseState::Before(node) => {
// progress_bar.inc(1);
// visited.insert(node.clone());
// start_times.insert(node, time);
// time += 1;
// // it is extremely important that this before the adjacencies to correctly
// // iterate over the graph
// if let Some(adjacencies) = self.get_adjacencies(node) {
// for adj in adjacencies {
// println!("Node: {:?} Adj: {:?}", node, adj,);
// stack.push(RecurseState::AfterNeighbor(node));
// if !visited.contains(adj) {
// edge_types.insert((node, adj), EdgeType::TreeEdge);
// stack.push(RecurseState::Before(adj));
// } else {
// stack.push(RecurseState::BeforeNeighbor(node, adj));
// }
// }
// }
// }
// RecurseState::AfterNeighbor(node) => {
// finished_nodes.insert(node);
// time += 1;
// }
// RecurseState::BeforeNeighbor(node, adj) => {
// let start_time_node = start_times.get(node).unwrap();
// let start_time_adj = start_times.get(adj).unwrap();
// let end_time_node = finished_nodes.get(node).unwrap_or(&0);
// let end_time_adj = finished_nodes.get(adj).unwrap_or(&0);
// println!(
// "Times: ({:?}, {:?}) ({:?}, {:?})",
// start_time_node, end_time_node, start_time_adj, end_time_adj
// );
// match (
// start_time_node.cmp(start_time_adj),
// end_time_node.cmp(end_time_adj),
// ) {
// (Ordering::Less, Ordering::Greater) => {
// edge_types.insert((node, adj), EdgeType::ForwardEdge);
// }
// (Ordering::Greater, Ordering::Less) => {
// edge_types.insert((node, adj), EdgeType::BackEdge);
// }
// _ => {
// edge_types.insert((node, adj), EdgeType::CrossEdge);
// }
// }
// }
// }
// }
// }
// edge_types
// }
}

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