General

# Author Problem Lang Verdict Time Memory Sent Judged
122490576 Contestant:
sansen
1550E - 11 Rust Accepted 1450 ms 35824 KB 2021-07-14 18:40:17 2021-07-15 09:52:50

→ Source
// ---------- begin chmin, chmax ----------
pub trait ChangeMinMax {
fn chmin(&mut self, x: Self) -> bool;
fn chmax(&mut self, x: Self) -> bool;
}

impl<T: PartialOrd> 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 ----------
// ---------- begin super slice ----------
pub trait SuperSlice {
type Item;
fn lower_bound(&self, key: &Self::Item) -> usize
where
Self::Item: Ord;
fn lower_bound_by<F>(&self, f: F) -> usize
where
F: FnMut(&Self::Item) -> std::cmp::Ordering;
fn lower_bound_by_key<K, F>(&self, key: &K, f: F) -> usize
where
K: Ord,
F: FnMut(&Self::Item) -> K;
fn upper_bound(&self, key: &Self::Item) -> usize
where
Self::Item: Ord;
fn upper_bound_by<F>(&self, f: F) -> usize
where
F: FnMut(&Self::Item) -> std::cmp::Ordering;
fn upper_bound_by_key<K, F>(&self, key: &K, f: F) -> usize
where
K: Ord,
F: FnMut(&Self::Item) -> K;
}

impl<T> SuperSlice for [T] {
type Item = T;
fn lower_bound(&self, key: &Self::Item) -> usize
where
T: Ord,
{
self.lower_bound_by(|p| p.cmp(key))
}
fn lower_bound_by<F>(&self, mut f: F) -> usize
where
F: FnMut(&Self::Item) -> std::cmp::Ordering,
{
self.binary_search_by(|p| f(p).then(std::cmp::Ordering::Greater))
.unwrap_err()
}
fn lower_bound_by_key<K, F>(&self, key: &K, mut f: F) -> usize
where
K: Ord,
F: FnMut(&Self::Item) -> K,
{
self.lower_bound_by(|p| f(p).cmp(key))
}
fn upper_bound(&self, key: &Self::Item) -> usize
where
T: Ord,
{
self.upper_bound_by(|p| p.cmp(key))
}
fn upper_bound_by<F>(&self, mut f: F) -> usize
where
F: FnMut(&Self::Item) -> std::cmp::Ordering,
{
self.binary_search_by(|p| f(p).then(std::cmp::Ordering::Less))
.unwrap_err()
}
fn upper_bound_by_key<K, F>(&self, key: &K, mut f: F) -> usize
where
K: Ord,
F: FnMut(&Self::Item) -> K,
{
self.upper_bound_by(|p| f(p).cmp(key))
}
}
// ---------- end super slice ----------
// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
(source = $s:expr,$($r:tt)*) => { let mut iter =$s.split_whitespace();
input_inner!{iter, $($r)*}
};
($($r:tt)*) => {
let s = {
let mut s = String::new();
s
};
let mut iter = s.split_whitespace();
input_inner!{iter, $($r)*}
};
}

macro_rules! input_inner {
($iter:expr) => {}; ($iter:expr, ) => {};
($iter:expr,$var:ident : $t:tt$($r:tt)*) => { let$var = read_value!($iter,$t);
input_inner!{$iter$($r)*} }; } macro_rules! read_value { ($iter:expr, ( $($t:tt),* )) => {
( $(read_value!($iter, $t)),* ) }; ($iter:expr, [ $t:tt ;$len:expr ]) => {
(0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>() }; ($iter:expr, chars) => {
read_value!($iter, String).chars().collect::<Vec<char>>() }; ($iter:expr, bytes) => {
read_value!($iter, String).bytes().collect::<Vec<u8>>() }; ($iter:expr, usize1) => {
read_value!($iter, usize) - 1 }; ($iter:expr, $t:ty) => {$iter.next().unwrap().parse::<\$t>().expect("Parse error")
};
}
// ---------- end input macro ----------

use std::io::Write;
use std::collections::*;

type Map<K, V> = BTreeMap<K, V>;
type Set<T> = BTreeSet<T>;
type Deque<T> = VecDeque<T>;

// 二分探索？
// 判定問題はbitdpっぽい感じで計算できそう
// 計算量雑に見積もっても logN * (kN + 2^k * k * logN)
// とかになりそうで厳しいような

fn run() {
input! {
n: usize,
k: usize,
s: bytes,
}
//    let s = vec![b'?'; n];
let mut sum = vec![vec![0; n + 1]; k];
for (i, c) in s.iter().enumerate().rev() {
for (j, sum) in sum.iter_mut().enumerate() {
sum[i] = sum[i + 1];
if *c == b'a' + j as u8 {
sum[i] += 1;
}
}
}
let mut trans = vec![vec![]; k];
let mut valid = |m: usize| -> bool {
if k * m > n {
return false;
}
trans.iter_mut().for_each(|p| p.clear());
for j in 0..=(n - m) {
let mut a = [0; 17];
let a = &mut a[..k];
for (a, sum) in a.iter_mut().zip(&sum) {
*a = sum[j] - sum[j + m];
}
let sum = a.iter().sum::<usize>();
for (i, a) in a.iter().enumerate() {
if *a == sum {
trans[i].push(j);
}
}
}
let mut dp = vec![n + 1; 1 << k];
dp[0] = 0;
for i in 0..(1 << k) {
let s = dp[i];
if s > n {
continue;
}
for (j, trans) in trans.iter().enumerate() {
if i >> j & 1 == 1 {
continue;
}
let x = trans.lower_bound(&s);
if x < trans.len() {
let t = trans[x] + m;
dp[i | (1 << j)].chmin(t);
}
}
}
dp[(1 << k) - 1] <= n
};
let mut ok = 0;
let mut ng = 1;
while valid(ng) {
ok = ng;
ng *= 2;
}
while ng - ok > 1 {
let mid = (ok + ng) / 2;
if valid(mid) {
ok = mid;
} else {
ng = mid;
}
}
println!("{}", ok);
}

fn main() {
run();
}


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