Submission #198391

#	Time	Username	Problem	Language	Result	Execution time	Memory
198391		alrad	Lampice (COCI19_lampice)	C++17	73 / 110	5074 ms	5856 KiB

lampice

#include <bits/stdc++.h>

using namespace std;

typedef unsigned long long ull;

const int N = 5e4 + 2;

vector<vector<int> > g(N , vector<int>());
int ans = 0;
string all;
string walk = "";

bool good(string cur) {
   string other = cur;
   reverse(other.begin() , other.end());
   return other == cur;
}

void dfs(int v , int p = -1) {
   walk.push_back(all[v - 1]);
   if (good(walk)) {
      ans = max(ans , (int)walk.size());
   }
   for (int to : g[v]) {
      if (to != p) {
         dfs(to , v);
         walk.pop_back();
      }
   }
}

//manacher

int getMaxPalindromic(string text) {
   int N = text.size();
    if(N == 0)
        return 0;
    N = 2*N + 1; //Position count
    int L[N]; //LPS Length Array
    L[0] = 0;
    L[1] = 1;
    int C = 1; //centerPosition
    int R = 2; //centerRightPosition
    int i = 0; //currentRightPosition
    int iMirror; //currentLeftPosition
    int maxLPSLength = 0;
    int maxLPSCenterPosition = 0;
    int start = -1;
    int end = -1;
    int diff = -1;

    for (i = 2; i < N; i++)
    {
        iMirror  = 2*C-i;
        L[i] = 0;
        diff = R - i;
        if(diff > 0)
            L[i] = min(L[iMirror], diff);
        while ( ((i + L[i]) < N && (i - L[i]) > 0) &&
            ( ((i + L[i] + 1) % 2 == 0) ||
            (text[(i + L[i] + 1)/2] == text[(i - L[i] - 1)/2] )))
        {
            L[i]++;
        }

        if(L[i] > maxLPSLength)
        {
            maxLPSLength = L[i];
            maxLPSCenterPosition = i;
        }
        if (i + L[i] > R)
        {
            C = i;
            R = i + L[i];
        }
    }
    start = (maxLPSCenterPosition - maxLPSLength)/2;
    end = start + maxLPSLength - 1;
    return end - start + 1;
}

vector<bool> lf(N , false);

void dfs1(int v , int p = -1) {
   walk.push_back(all[v - 1]);
   if (lf[v]) {
      int cur = getMaxPalindromic(walk);
      ans = max(ans , cur);
   }
   for (int to : g[v]) {
      if (to != p) {
         dfs1(to , v);
         walk.pop_back();
      }
   }
}

int main() {
   ios_base :: sync_with_stdio(0);
   cin.tie(0) , cout.tie(0);
   int n;
   cin >> n;
   cin >> all;
   bool subtask2 = true;
   for (int i = 1; i < n; i++) {
      int u , v;
      cin >> u >> v;
      if (u + 1 != v) {
         subtask2 = false;
      }
      g[u].push_back(v);
      g[v].push_back(u);
   }
   if (n <= 3000) {
      //solve subtask 1
      for (int i = 1; i <= n; i++) {
         walk = "";
         dfs(i);
      }
      cout << ans << '\n';
      return 0;
   }
   if (subtask2) {
      //solve subtask 2
      cout << getMaxPalindromic(all) << '\n';
      return 0;
   }
   vector<int> leafs;
   for (int i = 1; i <= n; i++) {
      if ((int)g[i].size() == 1) {
         leafs.push_back(i);
         lf[i] = true;
      }
   }
   for (int i = 0; i < (int)leafs.size(); i++) {
      walk = "";
      dfs1(leafs[i]);
   }
   cout << ans << '\n';
   return 0;
}

• Subtask 1: 17 / 17
• Subtask 2: 25 / 25
• Subtask 3: 31 / 31
• Subtask 4: 0 / 37