RosettaCodeData/Task/Topological-sort/Rust/topological-sort.rust

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use std::boxed::Box;
use std::collections::{HashMap, HashSet};
#[derive(Debug, PartialEq, Eq, Hash)]
struct Library<'a> {
name: &'a str,
children: Vec<&'a str>,
num_parents: usize,
}
fn build_libraries(input: Vec<&str>) -> HashMap<&str, Box<Library>> {
let mut libraries: HashMap<&str, Box<Library>> = HashMap::new();
for input_line in input {
let line_split = input_line.split_whitespace().collect::<Vec<&str>>();
let name = line_split.get(0).unwrap();
let mut num_parents: usize = 0;
for parent in line_split.iter().skip(1) {
if parent == name {
continue;
}
if !libraries.contains_key(parent) {
libraries.insert(
parent,
Box::new(Library {
name: parent,
children: vec![name],
num_parents: 0,
}),
);
} else {
libraries.get_mut(parent).unwrap().children.push(name);
}
num_parents += 1;
}
if !libraries.contains_key(name) {
libraries.insert(
name,
Box::new(Library {
name,
children: Vec::new(),
num_parents,
}),
);
} else {
libraries.get_mut(name).unwrap().num_parents = num_parents;
}
}
libraries
}
fn topological_sort<'a>(
mut libraries: HashMap<&'a str, Box<Library<'a>>>,
) -> Result<Vec<&'a str>, String> {
let mut needs_processing = libraries
.iter()
.map(|(k, _v)| k.clone())
.collect::<HashSet<&str>>();
let mut options: Vec<&str> = libraries
.iter()
.filter(|(_k, v)| v.num_parents == 0)
.map(|(k, _v)| *k)
.collect();
let mut sorted: Vec<&str> = Vec::new();
while !options.is_empty() {
let cur = options.pop().unwrap();
for children in libraries
.get_mut(cur)
.unwrap()
.children
.drain(0..)
.collect::<Vec<&str>>()
{
let child = libraries.get_mut(children).unwrap();
child.num_parents -= 1;
if child.num_parents == 0 {
options.push(child.name)
}
}
sorted.push(cur);
needs_processing.remove(cur);
}
match needs_processing.is_empty() {
true => Ok(sorted),
false => Err(format!("Cycle detected among {:?}", needs_processing)),
}
}
fn main() {
let input: Vec<&str> = vec![
"des_system_lib std synopsys std_cell_lib des_system_lib dw02 dw01 ramlib ieee\n",
"dw01 ieee dw01 dware gtech dw04\n",
"dw02 ieee dw02 dware\n",
"dw03 std synopsys dware dw03 dw02 dw01 ieee gtech\n",
"dw04 dw04 ieee dw01 dware gtech\n",
"dw05 dw05 ieee dware\n",
"dw06 dw06 ieee dware\n",
"dw07 ieee dware\n",
"dware ieee dware\n",
"gtech ieee gtech\n",
"ramlib std ieee\n",
"std_cell_lib ieee std_cell_lib\n",
"synopsys\n",
];
let libraries = build_libraries(input);
match topological_sort(libraries) {
Ok(sorted) => println!("{:?}", sorted),
Err(msg) => println!("{:?}", msg),
}
}