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Submission #530815

# Submission time Handle Problem Language Result Execution time Memory
530815 2022-02-26T21:15:08 Z Alex_tz307 Lampice (COCI19_lampice) C++17
25 / 110
 5000 ms 39972 KB 
#include <bits/stdc++.h>

using namespace std;

const int kN = 5e4;
const int mod = 1e9 + 9;
const int base = 29;
const int kM = (1 << 25) - 1;
string s;
vector<uint16_t> g[1 + kN];
uint16_t sz[1 + kN];
int p[1 + kN], h1[1 + kN], h2[1 + kN];
vector<uint16_t> centroids, nodes;
bitset<1 + kN> vis;
bitset<1 + kM> filter;
unordered_map<int, uint16_t> 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;
  filter[h1[u] & kM] = true;
  for (int v : g[u]) {
    if (!vis[v] && v != par) {
      dfs1(v, u, depth + 1);
    }
  }
}

bool dfs2(int u, int par, int depth, int len) {
  if (depth == len) {
    return h1[u] == h2[u];
  }
  nodes.emplace_back(u);
  preffixes[depth][h1[u]] -= 1;
  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 (filter[hsh & kM] && 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();
  preffixes[depth][h1[u]] += 1;
  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);
    }
  }
}

void removePaths(int u, int par, int depth) {
  if (preffixes[depth][h1[u]] > 0) {
    preffixes[depth][h1[u]] -= 1;
  }
  for (int v : g[u]) {
    if (!vis[v] && v != par) {
      removePaths(v, u, depth + 1);
    }
  }
}

bool solve(int u, int len) {
  for (int c : centroids) {
    vis[c] = true;
    dfs1(c, 0, 0);
    for (int v : g[c]) {
      if (!vis[v]) {
        nodes.clear();
        nodes.emplace_back(0);
        nodes.emplace_back(c);
        if (dfs2(v, c, 2, len)) {
          removePaths(c, 0, 1);
          return true;
        }
      }
    }
    removePaths(c, 0, 1);
  }
  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
0 / 17.0

# Verdict Execution time Memory Grader output
1 Incorrect 5 ms 4556 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 3482 ms 33656 KB Output is correct
2 Correct 2682 ms 33784 KB Output is correct
3 Correct 1614 ms 29380 KB Output is correct
4 Correct 2054 ms 30736 KB Output is correct
5 Correct 4035 ms 39972 KB Output is correct
6 Correct 201 ms 18368 KB Output is correct

Subtask #3
0 / 31.0

# Verdict Execution time Memory Grader output
1 Execution timed out 5051 ms 31808 KB Time limit exceeded
2 Halted 0 ms 0 KB -

Subtask #4
0 / 37.0

# Verdict Execution time Memory Grader output
1 Incorrect 5 ms 4556 KB Output isn't correct
2 Halted 0 ms 0 KB -