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use std::ops::*;
/// O(3^N)
pub fn zeta_subset<T: Clone + Add<Output = T>>(mut f: Vec<T>) -> Vec<T> {
let m = f.len();
for s in (0..m).rev() {
let mut t = s;
while t > 0 {
t = (t - 1) & s;
f[s] = f[s].clone() + f[t].clone();
}
}
f
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let n = 4;
let n2 = 1 << n;
let mut f = vec![0; n2 + 6];
for i in 0..n + 1 {
f[1 << i] = 1;
}
f = zeta_subset(f);
assert_eq!(
f,
[0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3,]
);
}
}