Submission #564939

#	Time	Username	Problem	Language	Result	Execution time	Memory
564939		ac2hu	Palindromes (APIO14_palindrome)	C++14	47 / 100	1097 ms	8012 KiB

palindrome

#include <bits/stdc++.h>
#ifdef DEBUG
#include "../templates/debug.h"
#else 
#define deb(x...)
#endif
using namespace std;
const int C = 26;
struct node{
    node* child[C];
    int cnt = 0;
    int dist = 0;
};
node* make_node(int d){
    node* temp = new node;
    for(int i = 0;i<C;i++){
        temp->child[i] = NULL;
    }
    temp->cnt = 0;
    temp->dist = d;
    return temp;
}
string s;
int ans = 1;
node* root1 = make_node(-1);
node* root2 = make_node(0);
auto is_pali(int l,int r){
    if(l > r)return true;
    if(s[l] != s[r])return false;
    return is_pali(l + 1, r - 1);
}
void add1(int l,int r){
    node* trav = root1;
    for(int i = l;i<=r;i++){
        int c = s[i] - 'a';
        if(!trav->child[c])
            trav->child[c] = make_node(trav->dist + 2);
        trav = trav->child[c];
        ++trav->cnt;
        ans = max(ans, trav->cnt*trav->dist);
    }
}
void add2(int l,int r){
    node* trav = root2;
    for(int i = l;i<=r;i++){
        int c = s[i] - 'a';
        if(!trav->child[c])
            trav->child[c] = make_node(trav->dist + 2);
        trav = trav->child[c];
        ++trav->cnt;
        ans = max(ans, trav->cnt*trav->dist);
    }
}
signed main(){
    cin >> s;
    int n = s.size();
    vector<int> leq(n,0);
    vector<int> req(n,0);
    for(int i = 1;i<n;i++){
        if(s[i] == s[i - 1])leq[i] = 1 + leq[i - 1];
    }
    for(int i = n - 2;i>=0;i--){
        if(s[i] == s[i + 1])req[i] = 1 + req[i + 1];
    }
    for(int i = 0;i<n;i++){
        auto check = [&](int mid)->bool{
            if(i - mid < 0)return false;
            if(i + mid > n - 1)return false;
            return is_pali(i - mid, i + mid);
        };
        int l = min(leq[i], req[i]) + 1,r = n;
        while(l<r){
            int mid = (l + r + 1)/2;
            if(check(mid)){
                l = mid;
            }
            else
                r = mid - 1;
        }
        if(check(l))
            add1(i,i + l);
        if(i > 0 && s[i] == s[i - 1]){
            l = min(leq[i - 1], req[i]) + 1,r = n - 1;
            while(l < r){
                int mid = (l + r + 1)/2;
                if(i - 1 - mid >= 0 && i + mid < n && is_pali(i - 1 - mid, i + mid)){
                    l = mid;
                }
                else
                    r = mid - 1;
            }
            if(i - 1 - l >=0 && i + l < n && is_pali(i - 1 - l,i + l))
                add2(i,i + l);
        }
    }
    vector<vector<int>> temp(26);
    for(int i = 0;i<n;i++){
        temp[s[i] - 'a'].push_back(req[i] + 1);
    }
    for(int j = 0;j<26;j++){
        vector<int> cc(n + 2, 0);
        for(auto e : temp[j]){
            cc[e + 1]--;
            cc[0]++;
        }
        for(int i = 1;i<=n + 1;i++)cc[i] += cc[i - 1];
        for(int i = 0;i<=n;i++){
            ans = max(ans, cc[i]*i);
        }
    }
    cout << ans << "\n";
}

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