Submission #868627

#	Time	Username	Problem	Language	Result	Execution time	Memory
868627		NeroZein	Valley (BOI19_valley)	C++17	100 / 100	161 ms	38964 KiB

valley

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

#ifdef Nero
#include "Deb.h"
#else
#define deb(...)
#endif

const int LOG = 18; 
const int N = 1e5 + 5;
const long long INF = 1e15;

int dep[N]; 
bool shop[N]; 
int pr[LOG][N];
vector<int> g[N]; 
long long dis[N]; 
array<int, 3> e[N]; 
long long dp[LOG][N];
int cnt, in[N], out[N];

void dfs(int v, int p) {
  in[v] = cnt++; 
  dp[0][v] = (shop[v] ? dis[v] : INF); 
  for (int i : g[v]) {
    int u = v ^ e[i][0] ^ e[i][1];
    if (u == p) continue;
    dep[u] = dep[v] + 1; 
    dis[u] = dis[v] + e[i][2]; 
    pr[0][u] = v; 
    for (int j = 1; j < LOG; ++j) {
      pr[j][u] = pr[j - 1][pr[j - 1][u]]; 
    }
    dfs(u, v); 
    dp[0][v] = min(dp[0][v], dp[0][u]); 
  }
  out[v] = cnt - 1; 
}

void init_dp(int v, int p) {
  for (int i : g[v]) {
    int u = v ^ e[i][0] ^ e[i][1];
    if (u == p) continue;
    for (int j = 1; j < LOG; ++j) {
      dp[j][u] = min(dp[j - 1][u], dp[j - 1][pr[j - 1][u]]);
    }
    init_dp(u, v); 
  }
}

bool isParent(int v, int u) {
  return in[v] <= in[u] && out[v] >= out[u]; 
}

long long get(int u, int v) {
  long long ret = INF;
  long long cc = dis[u];
  //deb(u) deb(v) deb(dp[0][v]) cout << '\n';
  for (int j = 0; j < LOG; ++j) {
    if ((dep[u] - dep[v]) >> j & 1) {
      ret = min(ret, dp[j][u] + cc);  
      u = pr[j][u]; 
    }
  }
  assert(u == v); 
  ret = min(ret, dp[0][u] + cc);
  return ret; 
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, s, q, ep;
  cin >> n >> s >> q >> ep;
  for (int i = 0; i < n - 1; ++i) {
    int u, v, w;
    cin >> u >> v >> w;
    e[i] = {u, v, w};
    g[u].push_back(i);
    g[v].push_back(i); 
  }
  for (int i = 0; i < s; ++i) {
    int v;
    cin >> v;
    shop[v] = true; 
  }
  dfs(ep, ep); 
  for (int i = 1; i <= n; ++i) {
    if (dp[0][i] != INF) {
      dp[0][i] -= 2 * dis[i];       
    }
  }
  init_dp(ep, ep); 
  while (q--) {
    int i, v;
    cin >> i >> v;
    --i;
    int qu = e[i][0];
    int qv = e[i][1];
    if (dis[qv] > dis[qu]) {
      swap(qv, qu); 
    }
    if (isParent(qu, v)) {
      long long ans = get(v, qu); 
      if (ans < INF) {
        cout << ans << '\n';
      } else {
        cout << "oo" << '\n'; 
      }
    } else {
      cout << "escaped" << '\n'; 
    }
  }
  return 0;
}

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