Submission #571413

#	Time	Username	Problem	Language	Result	Execution time	Memory
571413		Shin	Evacuation plan (IZhO18_plan)	C++14	100 / 100	568 ms	67048 KiB

plan

#include <bits/stdc++.h>
#define fi first
#define se second
#define mp make_pair
#define all(x) x.begin(), x.end()

using namespace std;
template <class X, class Y> bool minimize(X &a, Y b) {
    if (a > b) return a = b, true;
    return false;
}
template <class X, class Y> bool maximize(X &a, Y b) {
    if (a < b) return a = b, true;
    return false;
}

struct Disjoint_set {
    vector<int> lab;

    Disjoint_set(int n = 0) {
        lab.assign(n + 7, -1);
    }
    int root(int u) {
        return lab[u] < 0 ? u : lab[u] = root(lab[u]);
    }
    bool unite(int u, int v) {
        u = root(u); v = root(v);
        if (u == v) return false;
        if (lab[u] > lab[v]) swap(u, v);
        lab[u] += lab[v];
        lab[v] = u;
        return true;
    }
};

const int N = 5e5 + 7;
const int LOG = 20;

int n, m, num_npp;
int npp[N];
int ind[N];
int dist[N];
int depth[N];
int f[N][LOG + 1];
int par[N][LOG + 1];

bool flag[N];
vector<pair<int, int>> adj[N];
vector<int> g[N];

void shotest_path() {
  priority_queue<pair<int, int>> heap;
  memset(dist, 0x3f, sizeof dist);
  for (int i = 1; i <= num_npp; i ++) {
    heap.emplace(0, npp[i]);
    dist[npp[i]] = 0;
  }
  while (!heap.empty()) {
    int u, d_u; tie(d_u, u) = heap.top();
    heap.pop();
    d_u *= -1;
    if (dist[u] != d_u) {
      continue;
    }
    for (pair<int, int> v: adj[u]) if (minimize(dist[v.fi], d_u + v.se)) {
      heap.emplace(-d_u - v.se, v.fi);
    } 
  }
}

void dfs(int u, int p) {
  par[u][0] = p;
  f[u][0] = dist[u];
  for (int i = 1; i <= LOG; i ++) {
    par[u][i] = par[par[u][i - 1]][i - 1];
    f[u][i] = min(f[u][i - 1], f[par[u][i - 1]][i - 1]);
  }
  for (int v: g[u]) if (v != p) {
    depth[v] = depth[u] + 1;
    dfs(v, u);
  } 
}

int lca(int u, int v) {
  if (depth[v] > depth[u]) {
    swap(u, v);
  }
  int dist = depth[u] - depth[v], res = (int) 1e9;
  for (int i = LOG; i >= 0; i --) if ((dist >> i) & 1) {
    minimize(res, f[u][i]);
    u = par[u][i];
  }
  if (u == v) {
    return min(res, f[u][0]);
  }
  for (int i = LOG; i >= 0; i --) if (par[u][i] != par[v][i]) {
    minimize(res, f[u][i]);
    minimize(res, f[v][i]);
    u = par[u][i];
    v = par[v][i];
  }
  int w = par[u][0];
  minimize(res, f[w][0]);
  minimize(res, f[u][0]);
  return min(res, f[v][0]);
}

void build_tree() {
  iota(ind + 1, ind + n + 1, 1);
  sort(ind + 1, ind + n + 1, [&](int u, int v) {
    return dist[u] > dist[v];
  });
  Disjoint_set dsu(n);
  for (int i = 1; i <= n; i ++) {
    int u = ind[i];
    for (pair<int, int> v: adj[u]) {
      if (flag[v.fi]) {
        if (dsu.unite(u, v.fi)) {
          g[u].push_back(v.fi);
          g[v.fi].push_back(u);
        }
      }
    }
    flag[u] = true;
  }
  dfs(1, 1);
}

signed main() {
  cin.tie(0)->sync_with_stdio(0);
  cin >> n >> m;
  for (int i = 1; i <= m; i ++) {
    int u, v, w; cin >> u >> v >> w;
    adj[u].emplace_back(v, w);
    adj[v].emplace_back(u, w);
  } 
  cin >> num_npp;
  for (int i = 1; i <= num_npp; i ++) {
    cin >> npp[i];
  }
  shotest_path();
  build_tree();
  int q; cin >> q;
  while (q --) {
    int u, v; cin >> u >> v;
    cout << lca(u, v) << '\n';
  }
  return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 13 / 13
• Subtask 3: 12 / 12
• Subtask 4: 19 / 19
• Subtask 5: 46 / 46