Submission #933689

#	Time	Username	Problem	Language	Result	Execution time	Memory
933689		guagua0407	Palindromes (APIO14_palindrome)	C++17	73 / 100	1022 ms	31888 KiB

palindrome

#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define f first
#define s second
#define all(x) x.begin(),x.end()
#define _ ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

int dx[4]={0,0,1,-1};
int dy[4]={1,-1,0,0};

void setIO(string s) {
    freopen((s + ".in").c_str(), "r", stdin);
    freopen((s + ".out").c_str(), "w", stdout);
}

const ll p=29;
const ll mod=(1ll<<61)-1;
const int mxn=3e5+5;
ll powv[mxn];
ll hashr[mxn],hashl[mxn];
map<ll,int> mp;

void build(string str){
    int n=str.length();
    powv[0]=1;
    for(int i=1;i<=n;i++){
        powv[i]=(__int128)powv[i-1]*p%mod;
    }
    for(int i=1;i<n;i++){
        hashr[i]=((__int128)hashr[i-1]*p%mod+(str[i]-'a'+1))%mod;
    }
    for(int i=n-1;i>=1;i--){
        hashl[i]=((__int128)hashl[i+1]*p%mod+(str[i]-'a'+1))%mod;
    }
}

ll get1(int l,int r){
    ll ans=(hashl[l]-(__int128)hashl[r+1]*powv[r-l+1]%mod)%mod;
    if(ans<0) ans+=mod;
    return ans;
}

ll get2(int l,int r){
    ll ans=(hashr[r]-(__int128)hashr[l-1]*powv[r-l+1]%mod)%mod;
    if(ans<0) ans+=mod;
    return ans;
}

bool same(int l1,int r1,int l2,int r2){
    ll v1=get1(l1,r1);
    ll v2=get2(l2,r2);
    return v1==v2;
}

int main() {_
    string str;
    cin>>str;
    int n=(int)str.length();
    str="#"+str;
    build(str);
    priority_queue<pair<int,pair<int,int>>> pq;
    for(int i=1;i<=n;i++){
        {
            int l=0,r=min(i-1,n-i);
            while(l<r){
                int mid=(l+r+1)/2;
                if(same(i-mid,i-1,i+1,i+mid)){
                    l=mid;
                }
                else{
                    r=mid-1;
                }
            }
            ll val=get2(i-l,i+l);
            mp[val]++;
            if(mp[val]==1) pq.push({2*l+1,{i-l,i+l}});
        }
        {
            int l=0,r=min(i-1,n-i+1);
            while(l<r){
                int mid=(l+r+1)/2;
                if(same(i-mid,i-1,i,i+mid-1)){
                    l=mid;
                }
                else{
                    r=mid-1;
                }
            }
            if(l>0){
                ll val=get2(i-l,i+l-1);
                mp[val]++;
                if(mp[val]==1) pq.push({2*l,{i-l,i+l-1}});
            }
        }
    }
    ll ans=1;
    while(!pq.empty()){
        auto tmp=pq.top();
        pq.pop();
        int len=tmp.f;
        int l=tmp.s.f;
        int r=tmp.s.s;
        ll val=get2(l,r);
        ans=max(ans,1ll*mp[val]*len);
        l++;
        r--;
        if(l<=r){
            ll val2=get2(l,r);
            mp[val2]+=mp[val];
            if(mp[val2]==mp[val]) pq.push({r-l+1,{l,r}});
        }
    }
    cout<<ans<<'\n';
    return 0;
}
//maybe its multiset not set
//yeeorz
//laborz

Compilation message (stderr)

palindrome.cpp: In function 'void setIO(std::string)':
palindrome.cpp:15:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 |     freopen((s + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:16:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |     freopen((s + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 26 / 26
• Subtask 5: 0 / 27