Submission #1166056

#	Time	Username	Problem	Language	Result	Execution time	Memory
1166056		Sang	Palindromes (APIO14_palindrome)	C++20	100 / 100	89 ms	103848 KiB

palindrome

#include<bits/stdc++.h>
using namespace std;

#define int long long
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; i++)
#define FORD(i, a, b) for (int i = (a), _b = (b); i >= _b; i--)
#define fi first
#define se second
#define pb push_back
#define ALL(a) (a).begin(), (a).end()
#define task "kbsiudthw"

typedef vector<int> vi;
typedef pair<int, int> ii;
typedef pair<int, ii> pii;

const int N = 3e5 + 5;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 2277;

struct Node{
    int nxt[26], len, sufflink, cnt;
    vector<int> edges;
};

int len, num, suff;
string s;
Node tree[N];

bool addLetter(int pos){
    int cur = suff, curlen = 0;
    int let = s[pos] - 'a';

    while (1){
        curlen = tree[cur].len;
        if (pos - 1 - curlen >= 1 && s[pos-1-curlen] == s[pos]) break;
        cur = tree[cur].sufflink;
    }
    if (tree[cur].nxt[let]){
        suff = tree[cur].nxt[let];
        tree[tree[cur].nxt[let]].cnt++;
        return false;
    }

    ++num;
    suff = num;
    tree[num].len = tree[cur].len + 2;
    tree[cur].nxt[let] = num;
    tree[num].cnt = 1;

    if (tree[num].len == 1){
        tree[num].sufflink = 2;
        tree[2].edges.pb(num);
        return true;
    }

    while (true){
        cur = tree[cur].sufflink;
        curlen = tree[cur].len;
        if (pos - 1 - curlen >= 1 && s[pos-1-curlen] == s[pos]) {
            tree[num].sufflink = tree[cur].nxt[let];
            tree[tree[cur].nxt[let]].edges.pb(num);
            break;
        }
    }
    return 1;
}

void initTree(){
    num = 2; suff = 2;
    tree[1].len = -1; tree[1].sufflink = 1;
    tree[2].len = 0; tree[2].sufflink = 1;
    tree[1].edges.pb(2);
}

int dfs(int u){
    int ans = 0;
    for (int &v : tree[u].edges){
        ans = max(ans, dfs(v));
        tree[u].cnt += tree[v].cnt;
    }
    ans = max(ans, tree[u].len * tree[u].cnt);
    return ans;
}


signed main(){
    ios_base::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);
    }
    cin >> s;
    len = s.size(); s = ' ' + s;
    initTree();
    FOR (i, 1, len) {
        addLetter(i);
    }
    cout << dfs(1);

    return 0;
}

Compilation message (stderr)

palindrome.cpp: In function 'int main()':
palindrome.cpp:91:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   91 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:92:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   92 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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