Submission #711641

#	Time	Username	Problem	Language	Result	Execution time	Memory
711641		Pety	Pipes (CEOI15_pipes)	C++14	20 / 100	2585 ms	23432 KiB

pipes

#include <bits/stdc++.h>

using namespace std;

int n, m, x, y, sz[100002], p[100002], dp[20][100002], depth[100002];
vector<vector<int>>v[100002];
vector<int>G[100002];

int find (int x) {
  if (p[x] == x)
    return x;
  return p[x] = find(p[x]);
}

void merge (int x, int y) {
  int px = find(x);
  int py = find(y);
  if (px == py)
    return;

  if (sz[px] > sz[py]) {
    swap(x, y);
    swap(px, py);
  }
  p[px] = py;
  sz[py] += sz[px];
  for (int i = y; i; i = dp[0][i]) {
    for (int j = 0; (1 << j) < n; j++) {
      int lvl = (1 << j) - 1 - (depth[y] - depth[i]);
      if (lvl >= 0 && lvl < v[px].size()) 
        for (auto it : v[px][lvl])
          dp[j][it] = i;
    }
  }
  for (int i = 0; i < v[px].size(); i++) {
    while (depth[y] + i + 1 >= v[py].size())
      v[py].push_back({});
    for (auto it : v[px][i]) {
      v[py][depth[y] + i + 1].push_back(it);
      depth[it]+=depth[y] + 1;
    }
  }
}

int lca (int x, int y) {
  if (depth[x] > depth[y])
    swap(x, y);
  int d = depth[y] - depth[x];
  for (int i = 0; (1 << i) <= d; i++)
    if (d & (1 << i))
      y = dp[i][y];
  if (x == y)
    return x;
  for (int i = 19; i >= 0; i--)
    if (dp[i][x] != dp[i][y]) {
      x = dp[i][x];
      y = dp[i][y];
    }
  return dp[0][x];
}

int add[100002], viz[100002];

void dfs (int x, int par) {
  //cout << x << "\n";
  viz[x] = 1;
  for (auto it : G[x]) {
    if (it == par)
      continue;
    dfs(it, x);
    add[x] += add[it];
  }
  if (add[x] == 0 && par != 0)
    cout << x << " " << par << "\n";
}

int main () 
{
  ios_base::sync_with_stdio(false);
  cin.tie(0); cout.tie(0);
  cin >> n >> m;
  for (int i = 1; i <= n; i++) {
    p[i] = i;
    sz[i] = 1;
    v[i].push_back({i});
  }
  for (int i = 1; i <= m; i++) {
    cin >> x >> y;
    if (find(x) == find(y)) {
      int L = lca(x, y);
      add[L] -= 2;
      add[x]++;
      add[y]++;
    }
    else {
        G[x].push_back(y);
      G[y].push_back(x);
      merge(x, y);
    }
  }
  for (int i = 1; i <= n; i++)
    if (!viz[find(i)])
      dfs(find(i), 0);
  return 0;
}

Compilation message (stderr)

pipes.cpp: In function 'void merge(int, int)':
pipes.cpp:30:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   30 |       if (lvl >= 0 && lvl < v[px].size())
      |                       ~~~~^~~~~~~~~~~~~~
pipes.cpp:35:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   35 |   for (int i = 0; i < v[px].size(); i++) {
      |                   ~~^~~~~~~~~~~~~~
pipes.cpp:36:29: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   36 |     while (depth[y] + i + 1 >= v[py].size())
      |            ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10