Submission #536437

#	Time	Username	Problem	Language	Result	Execution time	Memory
536437		cig32	Valley (BOI19_valley)	C++17	100 / 100	155 ms	40436 KiB

valley

#include "bits/stdc++.h"
using namespace std;
const int MAXN = 2e5 + 10;
const int MOD = 120717661;
#define int long long
#define ll __int128
mt19937_64 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
int rnd(int x, int y) {
  int u = uniform_int_distribution<int>(x, y)(rng); return u;
}
ll read() { // read int128
  int x; cin >> x; return (ll)x;
}
long long bm(long long b, long long p) {
  if(p==0) return 1 % MOD;
  long long r = bm(b, p >> 1);
  if(p&1) return (((r*r) % MOD) * b) % MOD;
  return (r*r) % MOD;
}
long long inv(long long b) { 
  return bm(b, MOD-2);
}
long long f[MAXN];
long long nCr(int n, int r) { 
  long long ans = f[n]; ans *= inv(f[r]); ans %= MOD;
  ans *= inv(f[n-r]); ans %= MOD; return ans;
}
void precomp() { 
  for(int i=0; i<MAXN; i++) f[i] = (i == 0 ? 1 % MOD : (f[i-1] * i) % MOD);
}

vector<pair<int, int> > adj[MAXN];

int oh[MAXN];
int shop[MAXN];
int x, y; // edge removed
vector<pair<int, int> > edges;
int dep[MAXN];
int tin[MAXN], tout[MAXN];
int par[MAXN];
int wow = 0;
int sz[MAXN];
void dfs(int node, int prv, int cur) {
  oh[node] = 1e18;
  dep[node] = cur;
  tin[node] = ++wow;
  par[node] = prv;
  sz[node] = 1;
  for(auto x: adj[node]) {
    if(x.first != prv) {
      dfs(x.first, node, cur + x.second);
      oh[node] = min(oh[node], oh[x.first]);
      sz[node] += sz[x.first];
    }
  }
  tout[node] = ++wow;
  if(shop[node]) oh[node] = cur;
}

bool cmp(pair<int, int> a, pair<int, int> b) {
  return sz[a.first] > sz[b.first];
}
vector<int> euler2;
void dfs2(int node, int prv) {
  euler2.push_back(node);
  for(auto x: adj[node]) {
    if(x.first != prv) {
      dfs2(x.first, node);
    }
  }
}

int st[19][MAXN];

int query_min(int l, int r ) {
  int k = 32 - __builtin_clz(r-l+1) - 1;
  return min(st[k][l], st[k][r - (1<<k) + 1]);
}

void solve(int tc) {
  int n, s, q, e;
  cin >> n >> s >> q >> e;
  for(int i=1; i<n; i++) {
    int a, b, w;
    cin >> a >> b >> w;
    edges.push_back({a, b});
    adj[a].push_back({b, w});
    adj[b].push_back({a, w});
  }
  for(int i=0; i<s; i++) {
    int c; cin >> c;
    shop[c] = 1;
  }
  dfs(e, -1, 0);
  for(int i=1; i<=n; i++) sort(adj[i].begin(), adj[i].end(), cmp);
  dfs2(e, -1);
  for(int i=0; i<euler2.size(); i++) st[0][i] = oh[euler2[i]] - 2 * dep[euler2[i]];
  for(int i=1; i<19; i++) {
    for(int j=0; j<euler2.size(); j++) {
      if(j + (1<<i) - 1 < euler2.size()) {
        st[i][j] = min(st[i-1][j], st[i-1][j + (1<<(i-1))]);
      }
    }
  }
  int pos[n + 1], dage[n + 1]; // position in euler2 -> position of dage
  for(int i=0; i<n; i++) {
    pos[euler2[i]] = i;
  }
  for(int i=0; i<n; i++) {
    if(i == 0 || !(tin[euler2[i-1]] < tin[euler2[i]] && tout[euler2[i]] < tout[euler2[i-1]])) {
      dage[i] = i;
    }
    else {
      dage[i] = dage[i - 1];
    }
  }
  while(q--) {
    int i, r;
    cin >> i >> r;
    if(n == 1) {
      cout << "escaped\n";
      continue;
    }
    i--;
    x = edges[i].first, y = edges[i].second;
    if(tin[x] > tin[y]) swap(x, y);
    if(!(tin[y] <= tin[r] && tout[r] <= tout[y])) {
      cout << "escaped\n";
    }
    else {
      int og = r;
      int ans = 1e18;

      while(1) {
        int p = pos[r], en = dage[pos[r]];
        if(tin[euler2[en]] < tin[y]) en = pos[y];
        ans = min(ans, dep[og] + query_min(en, p));
        if(euler2[en] != y) r = par[euler2[en]];
        else break;
      }
      cout << (ans >= 1e14 ? "oo" : to_string(ans)) << "\n";
    }
  }
}
int32_t main(){
  ios::sync_with_stdio(0); cin.tie(0);
  int t = 1; //cin >> t;
  for(int i=1; i<=t; i++) solve(i);
}

Compilation message (stderr)

valley.cpp: In function 'void solve(long long int)':
valley.cpp:97:17: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   97 |   for(int i=0; i<euler2.size(); i++) st[0][i] = oh[euler2[i]] - 2 * dep[euler2[i]];
      |                ~^~~~~~~~~~~~~~
valley.cpp:99:19: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   99 |     for(int j=0; j<euler2.size(); j++) {
      |                  ~^~~~~~~~~~~~~~
valley.cpp:100:25: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  100 |       if(j + (1<<i) - 1 < euler2.size()) {
      |          ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~

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