Submission #1008034

#	Time	Username	Problem	Language	Result	Execution time	Memory
1008034		Zero_OP	Palindromes (APIO14_palindrome)	C++14	100 / 100	65 ms	59212 KiB

palindrome

#include<bits/stdc++.h>

using namespace std;
using int64 = int64_t;

#define  FOR(i, l, r) for(int i = (l), _r = (r); i <= _r; ++i)
#define FORD(i, r, l) for(int i = (r), _l = (l); i >= _l; --i)
#define  rep(i, l, r) for(int i = (l), _r = (r); i < _r; ++i)
#define repd(i, r, l) for(int i = (r) - 1, _l = l; i >= _l; --i)
#define          left __left
#define         right __right
#define          next __next
#define          prev __prev
#define           div __div
#define            pb push_back
#define            pf push_front
#define        all(v) v.begin(), v.end()
#define         sz(v) (int)v.size()
#define    compact(v) v.erase(unique(all(v)), end(v))
#define        dbg(v) "[" #v " = " << (v) << "]"
#define    file(name) if(fopen(name".inp", "r")) {freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }

template<typename T>
    bool minimize(T& a, const T& b){
        if(a > b) return a = b, true;
        return false;
    }

template<typename T>
    bool maximize(T& a, const T& b){
        if(a < b) return a = b, true;
        return false;
    }

template<int dimension, typename T>
struct vec : public vector<vec<dimension - 1, T>> {
    static_assert(dimension > 0, "Dimension must be positive !\n");
    template<typename... Args>
    vec(int n = 0, Args... args) : vector<vec<dimension - 1, T>> (n, vec<dimension - 1, T>(args...)) {}
};

template<typename T>
struct vec<1, T> : public vector<T> {
    vec(int n = 0, T val = T()) : vector<T>(n, val) {}
};

void preprocess();
void init();
void process();

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    file("antuvu");
    preprocess();

    int T = 1; //cin >> T;
    while(T--){
        init();
        process();
    }

    return 0;
}

// Palindrome Tree {{{
// Notes:
// - number of *distinct* palindrome substring <= N
// Tested:
// - https://oj.vnoi.info/problem/icpc22_mn_d
template<int MAXC = 26>
struct PalindromicTree {
    PalindromicTree(const string& str)
            : _sz(str.size() + 5),
              next(_sz, vector<int> (MAXC, 0)),
              link(_sz, 0), qlink(_sz, 0),
              cnt(_sz, 0), right_id(_sz, 0),
              len(_sz, 0), s(_sz, 0) {
        init();
        for (int i = 0; i < (int) str.size(); ++i) {
            add(str[i], i);
        }
        count();
    }
    int _sz;

    // returns vector of (left, right, frequency)
    vector<tuple<int,int,int>> get_palindromes() {
        vector<tuple<int,int,int>> res;
        dfs(0, res);
        dfs(1, res);
        return res;
    }

    void dfs(int u, vector<tuple<int,int,int>>& res) {
        if (u > 1) {  // u = 0 and u = 1 are two empty nodes
            res.emplace_back(right_id[u] - len[u] + 1, right_id[u], cnt[u]);
        }
        for (int i = 0; i < MAXC; ++i) {
            if (next[u][i]) dfs(next[u][i], res);
        }
    }

    int last, n, p;
    vector<vector<int>> next, dlink;
    vector<int> link, qlink, cnt, right_id, len, s;

    int newnode(int l, int right) {
        len[p] = l;
        right_id[p] = right;
        return p++;
    }
    void init() {
        p = 0;
        newnode(0, -1), newnode(-1, -1);
        n = last = 0;
        s[n] = -1, link[0] = 1;
    }
    int getlink(int x) {
        while (s[n - len[x] - 1] != s[n]) {
            if (s[n - len[link[x]] - 1] == s[n]) x = link[x];
            else x = qlink[x];
        }
        return x;
    }
    void add(char c, int right) {
        c -= 'a';
        s[++n] = c;
        int cur = getlink(last);
        if (!next[cur][(int) c]) {
            int now = newnode(len[cur] + 2, right);
            link[now] = next[getlink(link[cur])][(int) c];
            next[cur][(int) c] = now;
            if (s[n - len[link[now]]] == s[n - len[link[link[now]]]]) {
                qlink[now] = qlink[link[now]];
            }
            else {
                qlink[now] = link[link[now]];
            }
        }
        last = next[cur][(int) c];
        cnt[last]++;
    }
    void count() {
        for (int i = p - 1; i >= 0; i--) {
            cnt[link[i]] += cnt[i];
        }
    }
};
// }}}

void preprocess(){

}

void init(){

}

void process(){
    string s;
    cin >> s;

    PalindromicTree<26> T(s);
    vector<tuple<int, int, int>> p = T.get_palindromes();
    long long ans = 0;
    for(int i = 0; i < sz(p); ++i){
        int l, r, cnt;
        tie(l, r, cnt) = p[i];

        maximize(ans, 1ll * cnt * (r - l + 1));
    }
    cout << ans << '\n';
}

Compilation message (stderr)

palindrome.cpp: In function 'int main()':
palindrome.cpp:21:58: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 | #define    file(name) if(fopen(name".inp", "r")) {freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:55:5: note: in expansion of macro 'file'
   55 |     file("antuvu");
      |     ^~~~
palindrome.cpp:21:91: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 | #define    file(name) if(fopen(name".inp", "r")) {freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                                                    ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:55:5: note: in expansion of macro 'file'
   55 |     file("antuvu");
      |     ^~~~

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