結果

問題 No.2858 Make a Palindrome
ユーザー 沙耶花
提出日時 2024-08-25 14:20:03
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 481 ms / 3,000 ms
コード長 3,164 bytes
コンパイル時間 4,372 ms
コンパイル使用メモリ 257,780 KB
最終ジャッジ日時 2025-02-24 01:08:42
ジャッジサーバーID
(参考情報)
judge4 / judge3
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ファイルパターン 結果
other AC * 40
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ソースコード

diff #
プレゼンテーションモードにする

#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000001
struct rolling_hash{
long long t_hash;
static inline vector<long long> power;
static const long long MOD = (1LL<<61)-1;
static const long long b = 123456;
int sz;
rolling_hash(){
sz = 0;
t_hash = 0;
}
rolling_hash(char c){
sz = 1;
t_hash = b*c;
}
long long mul(__int128 x,__int128 y){
__int128 t = x*y;
t = (t>>61) + (t&MOD);
if(t>=MOD)t -= MOD;
return t;
}
long long get_pow(int sz){
if(power.size()>sz)return power[sz];
while(power.size()<=sz){
if(power.size()==0)power.push_back(1);
else power.push_back(mul(power.back(),b));
}
return power.back();
}
rolling_hash &operator+=(const rolling_hash &another){
(*this).t_hash = mul((*this).t_hash,get_pow(another.sz));
(*this).t_hash += another.t_hash;
if((*this).t_hash>=MOD)(*this).t_hash -= MOD;
(*this).sz += another.sz;
return (*this);
}
rolling_hash operator+(const rolling_hash &another)const{
return (rolling_hash(*this)+=another);
}
rolling_hash &operator-=(const rolling_hash &another){
(*this).t_hash += MOD - mul(another.t_hash,get_pow((*this).sz-another.sz));
if((*this).t_hash>=MOD)(*this).t_hash -= MOD;
(*this).sz -= another.sz;
return (*this);
}
rolling_hash operator-(const rolling_hash &another)const{
return (rolling_hash(*this)-=another);
}
bool operator<(const rolling_hash &another)const{
if((*this).t_hash!=another.t_hash)return (*this).t_hash<another.t_hash;
return (*this).sz<another.sz;
}
bool operator==(const rolling_hash &another)const{
return ((*this).t_hash==another.t_hash && (*this).sz==another.sz);
}
};
void solve(){
long long n,m;
cin>>n>>m;
string S;
cin>>S;
S = S+S+S+S;
vector<rolling_hash> h(n*4+1), rh(n*4+1);
//cout<<'a'<<endl;
rep(i,n*4){
h[i+1] = h[i]+rolling_hash(S[i]);
rh[i+1] = rh[i]+rolling_hash(S[n*4-i-1]);
}
//cout<<'b'<<endl;
long long ans = Inf64;
rep(i,n){
int ok = 0,ng = n+1;
while(ng-ok>1){
int mid = (ok+ng)/2;
int l = n+i;
int r = l+1;
l -= mid,r += mid;
if(h[r]-h[l]==rh[n*4-l]-rh[n*4-r])ok = mid;
else ng = mid;
}
if(ok==n||ok*2+1 >= m){
long long mm = m;
if(mm%2==0)mm++;
long long l = i - mm/2;
long long r = l + mm;
if(l<0){
long long D =-l;
D = (D+n-1)/n;
l += D*n, r+=D*n;
}
ans = min((r+n-1)/n, ans);
}
}
rep(i,n){
if(S[i]!=S[i+1])continue;
int ok = 0,ng = n+1;
while(ng-ok>1){
int mid = (ok+ng)/2;
int l = n+i;
int r = l+2;
l -= mid,r += mid;
if(h[r]-h[l]==rh[n*4-l]-rh[n*4-r])ok = mid;
else ng = mid;
}
if(ok==n||ok*2+2 >= m){
long long mm = m;
if(mm%2==1)mm++;
long long l = i - (mm-2)/2;
long long r = l + mm;
if(l<0){
long long D =-l;
D = (D+n-1)/n;
l += D*n, r+=D*n;
}
ans = min((r+n-1)/n, ans);
}
}
if(ans==Inf64)ans = -1;
cout<<ans<<endl;
}
int main(){
int _t;
cin>>_t;
rep(_,_t)solve();
return 0;
}
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