Submission #677873

#	Time	Username	Problem	Language	Result	Execution time	Memory
677873		Romiros	회문 (APIO14_palindrome)	C++17	47 / 100	1072 ms	17176 KiB

palindrome

#include <bits/stdc++.h>
 
#define ll long long
#define ld long double
#define vi vector<int>
#define pii pair<int, int>
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define ull H
 
using namespace std;
 
const int MAXN = 3e5 + 10;
 
const int MOD[2] = {(int)(1e9 + 7), (int)(1e9 + 9)};
 
struct H{
    ll h[2];
 
    H(int x = 0, int y = 0){
        h[0] = x;
        h[1] = y;
    }
};
 
H operator+(const H& a, const H& b){
    H c = a;
    for (int i = 0; i < 2; i++){
        c.h[i] = (a.h[i] + b.h[i]) % MOD[i];
    }
    return c;
}
 
H operator-(const H& a, const H& b){
    H c = a;
    for (int i = 0; i < 2; i++){
        c.h[i] = (a.h[i] - b.h[i] + MOD[i]) % MOD[i];
    }
    return c;
}
 
H operator*(const H& a, const H& b){
    H c = a;
    for (int i = 0; i < 2; i++){
        c.h[i] = (a.h[i] * 1ll * b.h[i]) % MOD[i];
    }
    return c;
}
 
bool operator==(const H& a, const H& b){
    for (int i = 0; i < 2; i++){
        if (a.h[i] != b.h[i]){
            return 0;
        }
    }
    return 1;
}

ull pw[MAXN + 10];
ull pref[MAXN];
ull suff[MAXN];
int n;
 
ull h(int i, int j){
    return (pref[j] - pref[i - 1]) * pw[MAXN - i + 1];
}
 
ull rh(int i, int j){
    return (suff[i] - suff[j + 1]) * pw[MAXN + j - n];
}
 
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    #ifdef ON_PC
        freopen("input.txt", "r", stdin);
    #endif
    // freopen("output.txt", "w", stdout);
    pw[0] = {1, 1};
    for (int i = 1; i < MAXN + 10; i++){
        pw[i] = pw[i - 1] * H{57, 113};
    }
    int T = 1;
    // cin >> T;
    while (T--){
        string s;
        cin >> s;
        n = s.size();   
        s = " " + s;
        for (int i = 1; i <= n; i++){
            pref[i] = pref[i - 1] + (s[i] - 'a' + 1) * pw[i - 1];
        }
        for (int i = n; i >= 1; i--){
            suff[i] = suff[i + 1] + (s[i] - 'a' + 1) * pw[n - i];
        }
        ll res = 0;
        for (int f = 0; f < 2; f++){
            vector<int> d(n + 1);
            for (int i = 1; i <= n; i++){
                int l = 0, r = min(i, n - (i + f) + 1) + 1;
                while (r - l > 1){
                    int m = (l + r) / 2;
                    if (rh(i - m + 1, i) == h(i + f, i + f + m - 1)){
                        l = m;
                    } else {
                        r = m;
                    }
                }
                d[i] = l;
            }
            for (int i = 1; i <= n; i++){
                res = max(res, (ll)(2 * d[i] - !f));
            }
            vector<int> order(n);
            for (int i = 1; i <= n; i++){
                order[i - 1] = i;
            }
            function<int(int, int)> lcp = [&](int i, int j){
                int l = 0, r = min(d[i], d[j]) + 1;
                while (r - l > 1){
                    int m = (l + r) / 2;
                    if (h(i - m + 1, i) == h(j - m + 1, j)){
                        l = m;
                    } else {
                        r = m;
                    }
                }
                return l;
            };
            sort(all(order), [&](int i, int j){
                int l = lcp(i, j);
                if (l == min(d[i], d[j])){
                    if (d[i] != d[j]){
                        return d[i] < d[j];
                    }
                    return i < j;
                }
                return s[i - l] < s[j - l];
            });
            vector<int> lcp_res(n);
            for (int i = 0; i + 1 < n; i++){
                lcp_res[i] = lcp(order[i], order[i + 1]);
            }
            vector<int> lb(n);
            vector<int> rb(n);
            vector<int> st;
            for (int i = 0; i < n; i++){
                while (!st.empty() && lcp_res[st.back()] >= lcp_res[i]){
                    st.pop_back();
                }
                lb[i] = 0;
                if (!st.empty()){
                    lb[i] = st.back() + 1;
                }
                st.push_back(i);
            }
            st.clear();
            for (int i = n - 1; i >= 0; i--){
                while (!st.empty() && lcp_res[st.back()] >= lcp_res[i]){
                    st.pop_back();
                }
                rb[i] = n - 1;
                if (!st.empty()){
                    rb[i] = st.back();
                }
                st.push_back(i);
            }
            st.clear();
            for (int i = 0; i < n; i++){
                res = max(res, (2 * lcp_res[i] - !f) * 1ll * (rb[i] - lb[i] + 1));
                // int mn = d[order[i]];
                // for (int j = i; j < n; j++){
                //     res = max(res, (j - i + 1) * 1ll * (2 * mn - !f));
                //     if (j + 1 < n){
                //         mn = min(mn, lcp_res[j]);
                //     }
                // }
            }
        }
        cout << res << "\n";
    }
    return 0;
}

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