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pub fn graph_bfs<F>(
g: &[Vec<usize>],
mut f: F,
src: usize,
) where
F: FnMut(usize, usize) -> bool,
{
let mut que = std::collections::VecDeque::new();
que.push_back(src);
while let Some(u) = que.pop_front() {
for &v in g[u].iter() {
if f(u, v) {
que.push_back(v);
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_atcoder_abc244_e() {
let cases = vec![
((4, 4, 4, 1, 3, 2, vec![(1, 2), (2, 3), (3, 4), (1, 4)]), 4),
(
(
6,
5,
10,
1,
2,
3,
vec![(2, 3), (2, 4), (4, 6), (3, 6), (1, 5)],
),
0,
),
(
(
10,
15,
20,
4,
4,
6,
vec![
(2, 6),
(2, 7),
(5, 7),
(4, 5),
(2, 4),
(3, 7),
(1, 7),
(1, 4),
(2, 9),
(5, 10),
(1, 3),
(7, 8),
(7, 9),
(1, 6),
(1, 2),
],
),
952504739,
),
];
for ((n, m, k, s, t, x, edges), ans) in cases {
let s = s - 1;
let t = t - 1;
let x = x - 1;
const B: usize = 1 << 11;
let encode =
|i: usize, u: usize, p: usize| -> usize { (p * n + u) * B + i };
const N: usize = 1 << 23;
let mut g = vec![vec![]; N];
for (u, v) in edges {
let u = u - 1;
let v = v - 1;
let p = if v == x { 1 } else { 0 };
let q = if u == x { 1 } else { 0 };
for i in 0..k {
for j in 0..2 {
let x = encode(i, u, j);
let y = encode(i + 1, v, j ^ p);
g[x].push(y);
let x = encode(i, v, j);
let y = encode(i + 1, u, j ^ q);
g[x].push(y);
}
}
}
let mut dp = vec![0; N];
let s = encode(0, s, 0);
dp[s] = 1;
const MOD: usize = 998_244_353;
let mut to_que = vec![false; N];
to_que[s] = true;
let mut f = |u: usize, v: usize| -> bool {
dp[v] += dp[u];
dp[v] %= MOD;
if to_que[v] {
false
} else {
to_que[v] = true;
true
}
};
graph_bfs(&g, &mut f, s);
let t = encode(k, t, 0);
assert_eq!(dp[t], ans);
}
}
}