結果

問題 No.2858 Make a Palindrome
ユーザー shobonvip
提出日時 2024-08-25 15:43:04
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 718 ms / 3,000 ms
コード長 2,870 bytes
コンパイル時間 4,069 ms
コンパイル使用メモリ 254,612 KB
最終ジャッジ日時 2025-02-24 01:33:57
ジャッジサーバーID
(参考情報)
judge1 / judge4
このコードへのチャレンジ
(要ログイン)
ファイルパターン 結果
other AC * 40
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

#include<bits/stdc++.h>
using namespace std;
//* ATCODER
#include<atcoder/all>
using namespace atcoder;
typedef modint998244353 mint;
//*/
/* BOOST MULTIPRECISION
#include<boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
//*/
typedef long long ll;
#define rep(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
#define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--)
template <typename T> bool chmin(T &a, const T &b) {
if (a <= b) return false;
a = b;
return true;
}
template <typename T> bool chmax(T &a, const T &b) {
if (a >= b) return false;
a = b;
return true;
}
template <typename T> T max(vector<T> &a){
assert(!a.empty());
T ret = a[0];
for (int i=0; i<(int)a.size(); i++) chmax(ret, a[i]);
return ret;
}
template <typename T> T min(vector<T> &a){
assert(!a.empty());
T ret = a[0];
for (int i=0; i<(int)a.size(); i++) chmin(ret, a[i]);
return ret;
}
template <typename T> T sum(vector<T> &a){
T ret = 0;
for (int i=0; i<(int)a.size(); i++) ret += a[i];
return ret;
}
vector< int > manacher(const string &s) {
vector< int > radius(s.size());
int i = 0, j = 0;
while(i < s.size()) {
while(i - j >= 0 && i + j < s.size() && s[i - j] == s[i + j]) {
++j;
}
radius[i] = j;
int k = 1;
while(i - k >= 0 && i + k < s.size() && k + radius[i - k] < j) {
radius[i + k] = radius[i - k];
++k;
}
i += k;
j -= k;
}
return radius;
}
int max_odd(string s) {
vector<int> targ = manacher(s);
int odd = max(targ) * 2 - 1;
return odd;
}
int max_even(string s) {
string t = "";
rep(i,0,(int)s.size()){
t += s[i];
t += '$';
}
t.pop_back();
int even = 0;
vector<int> tmp = manacher(t);
for (int i=1; i<(int)tmp.size(); i+=2){
even = max(even, tmp[i]/2*2);
}
return even;
}
int max_length_palindrome(string s){
return max(max_even(s), max_odd(s));
}
void solve(){
int n; cin >> n;
ll m; cin >> m;
string s; cin >> s;
if (max_length_palindrome(s) >= m){
cout << 1 << endl;
return;
}
string t1 = s;
string t2 = s;
t2 += s;
string t3 = s;
t3 += s;
t3 += s;
string t4 = s;
t4 += s;
t4 += s;
t4 += s;
if (max_length_palindrome(t2) >= m){
cout << 2 << endl;
return;
}
if (max_length_palindrome(t3) >= m){
cout << 3 << endl;
return;
}
if (max_length_palindrome(t3) >= m){
cout << 3 << endl;
return;
}
if (max_length_palindrome(t2) == max_length_palindrome(t3)){
cout << -1 << endl;
return;
}
ll a1 = - max_length_palindrome(t2) + max_length_palindrome(t3);
ll b1 = max_length_palindrome(t2); // 2
ll f1 = (m - b1 + a1 - 1) / a1 + 2;
cout << f1 << endl;
/*
ll a2 = - max_length_palindrome(t2) + max_length_palindrome(t4);
ll b2 = max_length_palindrome(t2); // 3
ll f2 = (m - b2 + a2 - 1) / a2 * 2 + 3;
cout << f2 << endl;
*/
}
int main(){
int t; cin >> t;
while(t--) solve();
}
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