Submission #290523

#	Time	Username	Problem	Language	Result	Execution time	Memory
290523		VROOM_VARUN	Valley (BOI19_valley)	C++14	0 / 100	3 ms	640 KiB

valley

/*
ID: varunra2
LANG: C++
TASK: valley
*/

#include <bits/stdc++.h>
using namespace std;

#ifdef DEBUG
#include "lib/debug.h"
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define debug_arr(...) \
  cerr << "[" << #__VA_ARGS__ << "]:", debug_arr(__VA_ARGS__)
#pragma GCC diagnostic ignored "-Wsign-compare"
//#pragma GCC diagnostic ignored "-Wunused-parameter"
//#pragma GCC diagnostic ignored "-Wunused-variable"
#else
#define debug(...) 42
#endif

#define EPS 1e-9
#define IN(A, B, C) assert(B <= A && A <= C)
#define INF (ll)1e15
#define MEM(a, b) memset(a, (b), sizeof(a))
#define MOD 1000000007
#define MP make_pair
#define PB push_back
#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define x first
#define y second

const double PI = acos(-1.0);
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> PII;
typedef map<int, int> MPII;
typedef multiset<int> MSETI;
typedef set<int> SETI;
typedef set<string> SETS;
typedef vector<ll> VI;
typedef vector<PII> VII;
typedef vector<VI> VVI;
typedef vector<string> VS;

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define trav(a, x) for (auto& a : x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
typedef vector<int> vi;
#pragma GCC diagnostic ignored "-Wsign-compare"
// util functions

int n, s, e, q;
vector<VII> adj;
VI tin;
VI tout;
int curtime = 0;
VI magic;
VI dist;
VVI parmq;
VI cmin;
vector<bool> shop;
VII edg;
VVI lca;
const int segsize = 20;  // change this when submitting
// e is the root

void init() {
  adj.resize(n);
  tin.resize(n);
  tout.resize(n);
  magic.resize(n);
  dist.resize(n);
  parmq.resize(n);
  cmin.resize(n);
  shop.resize(n);
  edg.resize(n - 1);
  lca.resize(n);
  for (int i = 0; i < n; i++) {
    parmq[i].resize(segsize);
    lca[i].resize(segsize);
    cmin[i] = INF;
  }
}

bool isAnc(int u, int v) {
  if (u == -1) return true;
  if (v == -1) return false;
  return tin[u] <= tin[v] and tout[u] >= tout[v];
}

void dfs_lca(int u, int v) {
  lca[u][0] = v;
  tin[u] = ++curtime;
  for (int i = 1; i < segsize; i++) {
    int to = lca[u][i - 1];
    if (to == -1)
      lca[u][i] = -1;
    else
      lca[u][i] = lca[to][i - 1];
  }
  for (auto& x : adj[u]) {
    if (x.x == v) continue;
    dfs_lca(x.x, u);
  }
  tout[u] = ++curtime;
}

void dfs_dist(int u, int v) {
  for (auto& x : adj[u]) {
    if (x.x == v) continue;
    dist[x.x] = dist[u] + x.y;
    dfs_dist(x.x, u);
  }
}

void dfs_magic(int u, int v) {
  for (auto& x : adj[u]) {
    if (x.x == v) continue;
    dfs_magic(x.x, u);
    cmin[u] = min(cmin[u], cmin[x.x]);
  }
  if (shop[u]) cmin[u] = dist[u];
  magic[u] = -2 * dist[u] + cmin[u];
}

void dfs_build_parmq(int u, int v) {
  parmq[u][0] = magic[u];

  for (int i = 1; i < segsize; i++) {
    int to = lca[u][i - 1];
    if (to == -1)
      parmq[u][i] = parmq[u][i - 1];
    else
      parmq[u][i] = min(parmq[u][i - 1], parmq[to][i - 1]);
  }
  for (auto& x : adj[u]) {
    if (x.x == v) continue;
    dfs_build_parmq(x.x, u);
  }
}

ll qry(int u, int v) {
  ll ret = INF;
  for (int i = segsize - 1; i >= 0; i--) {
    if (!isAnc(lca[u][i], v)) {
      ret = min(ret, parmq[u][i]);
      u = lca[u][i];
    }
  }
  ret = min(ret, min(magic[v], magic[u]));
  return ret;
}

int main() {
#ifndef ONLINE_JUDGE
  freopen("valley.in", "r", stdin);
  freopen("valley.out", "w", stdout);
#endif
  cin.sync_with_stdio(0);
  cin.tie(0);

  cin >> n >> s >> q >> e;
  e--;

  init();

  for (int i = 0; i < n - 1; i++) {
    int u, v, w;
    cin >> u >> v >> w;
    u--;
    v--;
    adj[u].PB(MP(v, w));
    adj[v].PB(MP(u, w));
    edg[i] = MP(u, v);
  }

  for (int i = 0; i < s; i++) {
    int c;
    cin >> c;
    c--;
    shop[c] = true;
  }


  dfs_lca(e, -1);    // got in and out times of each node
  dfs_dist(e, -1);   // got distances
  dfs_magic(e, -1);  // made the magic array

  // now we need to calculate

  dfs_build_parmq(e, -1);

  // for(int i = 0; i < q; i++) {

  // }

  for (int i = 0; i < q; i++) {
    int ind, r;
    cin >> ind >> r;
    ind--;
    r--;
    int u, v;
    u = edg[ind].x;
    v = edg[ind].y;
    if (dist[u] < dist[v]) swap(u, v);
    if (!isAnc(u, r)) {
      cout << "escaped\n";
    } else {
      ll ret = dist[r] + qry(r, u);
      if (shop[r]) ret = 0;
      if (ret <= INF / 10 + 1ll)
        cout << ret << '\n';
      else
        cout << "oo" << '\n';
    }
  }


  return 0;
}

Compilation message (stderr)

valley.cpp: In function 'int main()':
valley.cpp:159:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  159 |   freopen("valley.in", "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
valley.cpp:160:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  160 |   freopen("valley.out", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 9
• Subtask 2: 0 / 27
• Subtask 3: 0 / 23
• Subtask 4: 0 / 41