use std::io::Write; use std::collections::*; type Map = BTreeMap; type Set = BTreeSet; type Deque = VecDeque; fn main() { input! { n: usize, m: usize, k: u64, s: usize1, t: usize1, e: [(usize1, usize1); m], } if k % 2 == 1 { println!("Yes"); return; } let mut g = vec![vec![]; n]; for (a, b) in e { g[a].push(b); g[b].push(a); } if g[s].iter().any(|g| *g != t) || g[t].iter().any(|g| *g != s) { println!("Yes"); return; } if g[s].is_empty() { println!("No"); return; } let mut val = k + 1; for src in 0..n { let mut dp = vec![vec![k + 1; n]; 2]; dp[0][src] = 0; let mut deq = Deque::new(); deq.push_back((0, src)); while let Some((p, v)) = deq.pop_front() { let d = dp[p][v] + 1; for &u in g[v].iter() { if dp[p ^ 1][u].chmin(d) { deq.push_back((p ^ 1, u)); } } } val.chmin(dp[1][src]); } if 3 + val <= k { println!("Yes"); } else { println!("No"); } } // ---------- begin input macro ---------- // reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 #[macro_export] macro_rules! input { (source = $s:expr, $($r:tt)*) => { let mut iter = $s.split_whitespace(); input_inner!{iter, $($r)*} }; ($($r:tt)*) => { let s = { use std::io::Read; let mut s = String::new(); std::io::stdin().read_to_string(&mut s).unwrap(); s }; let mut iter = s.split_whitespace(); input_inner!{iter, $($r)*} }; } #[macro_export] macro_rules! input_inner { ($iter:expr) => {}; ($iter:expr, ) => {}; ($iter:expr, $var:ident : $t:tt $($r:tt)*) => { let $var = read_value!($iter, $t); input_inner!{$iter $($r)*} }; } #[macro_export] macro_rules! read_value { ($iter:expr, ( $($t:tt),* )) => { ( $(read_value!($iter, $t)),* ) }; ($iter:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($iter, $t)).collect::>() }; ($iter:expr, chars) => { read_value!($iter, String).chars().collect::>() }; ($iter:expr, bytes) => { read_value!($iter, String).bytes().collect::>() }; ($iter:expr, usize1) => { read_value!($iter, usize) - 1 }; ($iter:expr, $t:ty) => { $iter.next().unwrap().parse::<$t>().expect("Parse error") }; } // ---------- end input macro ---------- // ---------- begin chmin, chmax ---------- pub trait ChangeMinMax { fn chmin(&mut self, x: Self) -> bool; fn chmax(&mut self, x: Self) -> bool; } impl ChangeMinMax for T { fn chmin(&mut self, x: Self) -> bool { *self > x && { *self = x; true } } fn chmax(&mut self, x: Self) -> bool { *self < x && { *self = x; true } } } // ---------- end chmin, chmax ----------