LeetCode 1059. All Paths from Source Lead to Destination

Problem Statement

use std::collections::{HashMap, HashSet};

impl Solution {
    fn dfs(g: &HashMap<i32, HashSet<i32>>, i: i32, des: i32, visited: &mut HashMap<i32, i32>) -> bool {
        if !g.contains_key(&i) || g.get(&i).unwrap().is_empty() {
            return i == des;
        }
        if visited.contains_key(&i) {
            let val = visited.get(&i).unwrap();
            if *val == 1 {
                return false;
            }
            if *val == -1 {
                return true;
            }
        } else {
            visited.insert(i, 1);
        }
        for neib in g.get(&i).unwrap() {
            if !Self::dfs(g, *neib, des, visited) {
                return false;
            }
        }
        visited.insert(i, -1);
        return true;
    }

    pub fn leads_to_destination(n: i32, edges: Vec<Vec<i32>>, source: i32, destination: i32) -> bool {
        let (mut g, mut visited) = (HashMap::new(), HashMap::new());
        for e in edges {
            if !g.contains_key(&e[0]) {
                g.insert(e[0], HashSet::new());
            }
            let mut val = g.get(&e[0]).unwrap().clone();
            val.insert(e[1]);
            g.insert(e[0], val);
        }
        return Self::dfs(&g, source, destination, &mut visited);
    }
}