Submission #601355

#	Time	Username	Problem	Language	Result	Execution time	Memory
601355		narvalo	Ferries (NOI13_ferries)	C++17	17 / 40	144 ms	19144 KiB

ferries

#include <bits/stdc++.h>

using namespace std;

const int INF = (int)1e9;

int ferries(int n , int m , vector<int> a , vector<int> b , vector<int> c) {
  vector<vector<pair<int , int>>> adj(n);
  for (int i = 0 ; i < m ; i++) {
    a[i] -= 1 , b[i] -= 1;
    adj[a[i]].emplace_back(b[i] , c[i]);
  }
  vector<int> dp(n , -1) , vis(n);
  function<int(int)> Solve = [&](int node) {
    if (node == n - 1) {
      return 0;
    }
    if (vis[node] == 1) {
      return -1;
    }
    if (dp[node] != -1) {
      return dp[node];
    }
    vis[node] = 1;
    vector<int> d , s;
    for (auto x : adj[node]) {
      int g = Solve(x.first);
      if (g != -1 && g != INF) {
        d.emplace_back(g);
        s.emplace_back(x.second);
      }
    }
    sort(d.begin() , d.end());
    sort(s.begin() , s.end());
    auto Get = [&]() {
      int val = INF;
      for (int i = 0 ; i < (int)s.size() ; i += 1) {
        val = min(val , s[i] + d[(int)s.size() - i - 1]);
      }
      return val;
    };
    int res = Get();
    reverse(s.begin() , s.end());
    reverse(d.begin() , d.end());
    res = max(res , Get());
    vis[node] = 2;
    return dp[node] = res;
  };
  int res = Solve(0);
  return res;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n , m;
  cin >> n >> m;
  vector<int> a(m) , b(m) , c(m);
  for (int i = 0 ; i < m ; i += 1) {
    cin >> a[i] >> b[i] >> c[i];
  }
  cout << ferries(n , m , a , b , c) << '\n';
}

• Subtask 1: 7 / 7
• Subtask 2: 10 / 10
• Subtask 3: 0 / 11
• Subtask 4: 0 / 12