Submission #1055660

#	Time	Username	Problem	Language	Result	Execution time	Memory
1055660		RiverFlow	Palindromes (APIO14_palindrome)	C++14	47 / 100	1069 ms	7216 KiB

palindrome

#include <bits/stdc++.h>

#define nl "\n"
#define no "NO"
#define yes "YES"
#define fi first
#define se second
#define vec vector
#define task "main"
#define _mp make_pair
#define ii pair<int, int>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define evoid(val) return void(std::cout << val)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FOD(i, b, a) for(int i = (b); i >= (a); --i)
#define unq(x) sort(all(x)); x.resize(unique(all(x)) - x.begin())

using namespace std;

template<typename U, typename V> bool maxi(U &a, V b) {
    if (a < b) { a = b; return 1; } return 0;
}
template<typename U, typename V> bool mini(U &a, V b) {
    if (a > b) { a = b; return 1; } return 0;
}

const int N = (int)2e5 + 9;
const int mod = (int)1e9 + 7;

void prepare(); void main_code();

int main() {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    const bool MULTITEST = 0; prepare();
    int num_test = 1; if (MULTITEST) cin >> num_test;
    while (num_test--) { main_code(); }
}

void prepare() {};

struct trie {
    int cnt = 0;
    trie *child[26];
};
trie *new_node() {
    trie *n = new trie;
    FOR(i, 0, 25) n -> child[i] = NULL;
    return n;
}

int ins(trie* &r, char c) {
    if (r->child[c-'a']==NULL)
        r->child[c-'a']=new_node();
    r=r->child[c-'a'];
    ++r->cnt;
    return r->cnt;
}

void main_code() {
    trie *odd_root = new_node();
    trie *even_root = new_node();

    string s; cin >> s;
    int n = sz(s);
    int ans = 0;
    for(int i = 0; i < n; ++i) {
        trie *r = odd_root;
        for(int j = 0; j < min(i+1, n-i); ++j) {
            if (s[i-j] != s[i+j]) break ;
            int p = ins(r, s[i-j]);
            ans = max(ans, (2 * j + 1) * p);
        }
        r = even_root;
        for(int j = 0; j < min(i+1, n-i-1); ++j) {
            if (s[i-j] != s[i+j+1]) break ;
            int p = ins(r, s[i-j]);
            ans = max(ans, 2 * (j + 1) * p);
        }
    }
    cout << ans;
}


/*     Let the river flows naturally     */

Compilation message (stderr)

palindrome.cpp: In function 'int main()':
palindrome.cpp:36:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:37:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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