oj.uz

Submission #530250

# Submission time Handle Problem Language Result Execution time Memory
530250 2022-02-24T21:39:43 Z Alex_tz307 Lampice (COCI19_lampice) C++17
42 / 110
 5000 ms 35040 KB 
#include <bits/stdc++.h>

using namespace std;

const int kN = 5e4;
const int mod = 1e9 + 9;
const int base = 29;
string s;
vector<int> g[1 + kN];
int p[1 + kN], sz[1 + kN], h1[1 + kN], h2[1 + kN];
vector<int> centroids, nodes;
bitset<1 + kN> vis;
unordered_map<int, int> preffixes[kN];

void addSelf(int &x, const int &y) {
  x += y;
  if (x >= mod) {
    x -= mod;
  }
}

int add(int x, const int &y) {
  addSelf(x, y);
  return x;
}

void multSelf(int &x, const int &y) {
  x = (int64_t)x * y % mod;
}

int mult(int x, const int &y) {
  multSelf(x, y);
  return x;
}

void precalc() {
  p[0] = 1;
  for (int i = 1; i <= kN; ++i) {
    p[i] = mult(p[i - 1], base);
  }
}

void findSize(int u, int par) {
  sz[u] = 1;
  for (int v : g[u]) {
    if (!vis[v] && v != par) {
      findSize(v, u);
      sz[u] += sz[v];
    }
  }
}

int findCentroid(int u, int par, int n) {
  for (int v : g[u]) {
    if (!vis[v] && v != par && sz[v] > n / 2) {
      return findCentroid(v, u, n);
    }
  }
  return u;
}

void dfs1(int u, int par, int depth) {
  h1[u] = add(mult(h1[par], base), s[u] - 'a' + 1);
  h2[u] = add(h2[par], mult(p[depth], s[u] - 'a' + 1));
  preffixes[depth + 1][h1[u]] += 1;
  for (int v : g[u]) {
    if (!vis[v] && v != par) {
      dfs1(v, u, depth + 1);
    }
  }
}

void modifyPaths(int u, int par, int depth, int t) {
  preffixes[depth][h1[u]] += t;
  for (int v : g[u]) {
    if (!vis[v] && v != par) {
      modifyPaths(v, u, depth + 1, t);
    }
  }
}

bool dfs2(int u, int par, int depth, int len) {
  if (depth == len) {
    return h1[u] == h2[u];
  }
  nodes.emplace_back(u);
  int d = len - depth + 1;
  if (d <= depth) {
    int split = nodes[nodes.size() - d];
    if (h1[split] == h2[split]) {
      split = nodes[nodes.size() - d - 1];
      int hsh = add(h1[u], mod - mult(p[d], h1[split]));
      if (preffixes[d][hsh] > 0) {
        return true;
      }
    }
  }
  for (int v : g[u]) {
    if (!vis[v] && v != par && dfs2(v, u, depth + 1, len)) {
      return true;
    }
  }
  nodes.pop_back();
  return false;
}

void build(int u) {
  findSize(u, 0);
  int c = findCentroid(u, 0, sz[u]);
  centroids.emplace_back(c);
  vis[c] = true;
  for (int v : g[c]) {
    if (!vis[v]) {
      build(v);
    }
  }
}

bool solve(int u, int len) {
  for (int c : centroids) {
    dfs1(c, 0, 0);
    for (int v : g[c]) {
      if (!vis[v]) {
        modifyPaths(v, c, 2, -1);
        nodes.clear();
        nodes.emplace_back(0);
        nodes.emplace_back(c);
        if (dfs2(v, c, 2, len)) {
          modifyPaths(v, c, 2, 1);
          modifyPaths(c, 0, 1, -1);
          return true;
        }
        modifyPaths(v, c, 2, 1);
      }
    }
    modifyPaths(c, 0, 1, -1);
    vis[c] = true;
  }
  return false;
}

bool check(int n, int len) {
  bool ret = solve(1, len);
  for (int v = 1; v <= n; ++v) {
    vis[v] = false;
  }
  return ret;
}

void testCase() {
  int n;
  cin >> n >> s;
  s = '$' + s;
  bool ok2 = false;
  for (int i = 1; i < n; ++i) {
    int u, v;
    cin >> u >> v;
    g[u].emplace_back(v);
    g[v].emplace_back(u);
    if (s[u] == s[v]) {
      ok2 = true;
    }
  }
  build(1);
  for (int v = 1; v <= n; ++v) {
    vis[v] = false;
  }
  int l = 1, r = (n - 1) / 2, ans1 = 1;
  while (l <= r) {
    int mid = (l + r) / 2;
    if (check(n, 2 * mid + 1)) {
      ans1 = 2 * mid + 1;
      l = mid + 1;
    } else {
      r = mid - 1;
    }
  }
  int ans2 = 0;
  l = 2, r = n / 2;
  while (l <= r) {
    int mid = (l + r) / 2;
    if (check(n, 2 * mid)) {
      ans2 = 2 * mid;
      l = mid + 1;
    } else {
      r = mid - 1;
    }
  }
  cout << max({1 + ok2, ans1, ans2}) << '\n';
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  precalc();
  int tests = 1;
  for (int tc = 0; tc < tests; ++tc) {
    testCase();
  }
  return 0;
}

Subtask #1
17.0 / 17.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 4480 KB Output is correct
2 Correct 11 ms 4428 KB Output is correct
3 Correct 35 ms 4812 KB Output is correct
4 Correct 43 ms 4684 KB Output is correct
5 Correct 2 ms 4428 KB Output is correct
6 Correct 3 ms 4428 KB Output is correct
7 Correct 3 ms 4428 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 3983 ms 29948 KB Output is correct
2 Correct 2883 ms 29008 KB Output is correct
3 Correct 1639 ms 24624 KB Output is correct
4 Correct 2155 ms 26136 KB Output is correct
5 Correct 4207 ms 35040 KB Output is correct
6 Correct 162 ms 13576 KB Output is correct

Subtask #3
0 / 31.0

# Verdict Execution time Memory Grader output
1 Execution timed out 5084 ms 27968 KB Time limit exceeded
2 Halted 0 ms 0 KB -

Subtask #4
0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 4480 KB Output is correct
2 Correct 11 ms 4428 KB Output is correct
3 Correct 35 ms 4812 KB Output is correct
4 Correct 43 ms 4684 KB Output is correct
5 Correct 2 ms 4428 KB Output is correct
6 Correct 3 ms 4428 KB Output is correct
7 Correct 3 ms 4428 KB Output is correct
8 Correct 3983 ms 29948 KB Output is correct
9 Correct 2883 ms 29008 KB Output is correct
10 Correct 1639 ms 24624 KB Output is correct
11 Correct 2155 ms 26136 KB Output is correct
12 Correct 4207 ms 35040 KB Output is correct
13 Correct 162 ms 13576 KB Output is correct
14 Execution timed out 5084 ms 27968 KB Time limit exceeded
15 Halted 0 ms 0 KB -