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pub fn max_clique(adj_bits: &[usize]) -> usize {
let g = adj_bits;
let n = g.len();
let mut mx = 0;
for s in 0..1 << n {
let mut cnt = 0;
let mut t = s;
for i in 0..n {
if s >> i & 1 == 0 {
continue;
}
cnt += 1;
t &= g[i] | 1 << i;
}
if t == s {
mx = mx.max(cnt);
}
}
mx
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
// ref: https://atcoder.jp/contests/abc002/tasks/abc002_4
let cases = vec![
((5, vec![(1, 2), (2, 3), (1, 3)]), 3),
((5, vec![(1, 2), (2, 3), (3, 4)]), 2),
(
(
7,
vec![
(1, 2),
(1, 3),
(2, 3),
(4, 5),
(4, 6),
(4, 7),
(5, 6),
(5, 7),
(6, 7),
],
),
4,
),
((12, vec![]), 1),
];
for ((n, edges), ans) in cases {
let mut g = vec![0; n];
for (u, v) in edges {
let u = u - 1;
let v = v - 1;
g[u] |= 1 << v;
g[v] |= 1 << u;
}
assert_eq!(max_clique(&g), ans);
}
}
}