Submission #2376321

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Source Code Expand

use std::collections::BTreeMap;
use std::collections::BTreeSet;
use std::collections::VecDeque;

fn main() {
    let mut sc = Scanner::new();
    let n: usize = sc.read();
    let m: usize = sc.read();
    let mut graph = vec![vec![]; n];
    for _ in 0..m {
        let p = sc.read::<usize>() - 1;
        let q = sc.read::<usize>() - 1;
        let c: u32 = sc.read();
        graph[p].push((q, c));
        graph[q].push((p, c));
    }

    let mut dist = BTreeMap::new();
    let mut q = VecDeque::new();
    for &(to, company) in &graph[0] {
        q.push_back((to, 1, company));
        dist.insert((to, company), 1);
        dist.insert((0, company), 0);
    }

    let mut visit = BTreeSet::new();
    while !q.is_empty() {
        let (v, v_cost, company) = q.pop_front().unwrap();
        if v == n - 1 {
            println!("{}", v_cost);
            return;
        }
        if visit.contains(&(v, company)) {
            continue;
        }
        visit.insert((v, company));

        for &(to, next_company) in &graph[v] {
            let next_cost = if company == next_company {
                v_cost
            } else {
                v_cost + 1
            };
            match dist.get(&(to, next_company)) {
                Some(&cost) => if cost > next_cost {
                    assert_eq!(next_cost, v_cost);
                    dist.insert((to, next_company), next_cost);
                    q.push_front((to, next_cost, next_company));
                },
                _ => {
                    dist.insert((to, next_company), next_cost);
                    if next_cost > v_cost {
                        q.push_back((to, next_cost, next_company));
                    } else {
                        q.push_front((to, next_cost, next_company));
                    }
                }
            }
        }
    }

    println!("-1");
}

struct Scanner {
    ptr: usize,
    length: usize,
    buf: Vec<u8>,
    small_cache: Vec<u8>,
}

impl Scanner {
    fn new() -> Scanner {
        Scanner {
            ptr: 0,
            length: 0,
            buf: vec![0; 1024],
            small_cache: vec![0; 1024],
        }
    }

    fn load(&mut self) {
        use std::io::Read;
        let mut s = std::io::stdin();
        self.length = s.read(&mut self.buf).unwrap();
    }

    fn byte(&mut self) -> u8 {
        if self.ptr >= self.length {
            self.ptr = 0;
            self.load();
            if self.length == 0 {
                self.buf[0] = b'\n';
                self.length = 1;
            }
        }

        self.ptr += 1;
        return self.buf[self.ptr - 1];
    }

    fn is_space(b: u8) -> bool {
        b == b'\n' || b == b'\r' || b == b'\t' || b == b' '
    }

    fn read<T>(&mut self) -> T
    where
        T: std::str::FromStr,
        T::Err: std::fmt::Debug,
    {
        let mut b = self.byte();
        while Scanner::is_space(b) {
            b = self.byte();
        }

        for pos in 0..self.small_cache.len() {
            self.small_cache[pos] = b;
            b = self.byte();
            if Scanner::is_space(b) {
                return String::from_utf8_lossy(&self.small_cache[0..(pos + 1)])
                    .parse()
                    .unwrap();
            }
        }

        let mut v = self.small_cache.clone();
        while !Scanner::is_space(b) {
            v.push(b);
            b = self.byte();
        }
        return String::from_utf8_lossy(&v).parse().unwrap();
    }
}

Submission Info

Judge Result