Submission #827596

#	Time	Username	Problem	Language	Result	Execution time	Memory
827596		taher	Olympic Bus (JOI20_ho_t4)	C++17	37 / 100	1038 ms	6156 KiB

ho_t4

#include <bits/stdc++.h>
 
using namespace std;
 
#ifdef LOCAL
#include "C:\GCC\debug.h"
#else
#define debug(...) void(42)
#endif
 
const long long inf = 1165465792545;
const int N = 305;

vector<array<int, 4>> adj[N], inv[N];
long long d2[N][N], d1[N][N], dist[N];
long long between[N][N];
int count_edges[N][N];
int save_edge[N][N];

int cntA[N], cntB[N], cntC[N], cntD[N];
int middleA[N], middleB[N], middleC[N], middleD[N];
 
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
 
  int n, m;
  cin >> n >> m;

  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      between[i][j] = inf;
    }
  }
  vector<array<int, 4>> edges;
  for (int i = 0; i < m; i++) {
    int u, v;
    cin >> u >> v;
    int c, d;
    cin >> c >> d;
    --u, --v;
    adj[u].push_back({v, c, d, i});
    inv[v].push_back({u, c, d, i});
    edges.push_back({u, v, c, d});

    if (between[u][v] > c) {
      between[u][v] = c;
      count_edges[u][v] = 1;
      save_edge[u][v] = i;
    } else if (between[u][v] == c) {
      count_edges[u][v] += 1;
    }
  }
 
  array<int, 2> perm;
  perm[0] = 0;
  perm[1] = n - 1;

  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      d2[i][j] = inf;
      d1[i][j] = inf;
    }
  }
 
  auto Floyd = [&]() {
    for (int i = 0; i < n; i++) {
      d2[i][i] = 0;
      d1[i][i] = 0;
    }
    for (int i = 0; i < n; i++) {
      for (auto v : adj[i]) {
        d2[i][v[0]] = min(d2[i][v[0]], 1LL * v[1]);
        d1[i][v[0]] = min(d1[i][v[0]], 1LL * (v[1] + 1));
      }
    }
    for (int k = 0; k < n; k++) {
      for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
          d2[i][j] = min(d2[i][j], d2[i][k] + d2[k][j]);
          d1[i][j] = min(d1[i][j], d1[i][k] + d1[k][j]);
        }
      }
    }
  };
 
  Floyd();
  auto Update = [&](int forbidden, int source, int to, int cost) {
    for (int i = 0; i < n; i++) {
      dist[i] = inf;
    }

    set<int> alive;
    for (int i = 0; i < n; i++) {
      alive.insert(i);
    }

    dist[perm[1]] = 0;
    priority_queue<array<long long, 2>, vector<array<long long, 2>>, greater<array<long long, 2>>> que;
    que.push({0, perm[1]});

 
    while (!que.empty()) {
      auto cur = que.top();
      que.pop();
 
      if (dist[cur[1]] != cur[0]) {
        continue;
      }

      alive.erase(cur[1]);
 
      if (cur[1] == source) {
        if (dist[to] > 1LL * cur[0] + cost) {
          dist[to] = 1LL * cur[0] + cost;
          que.push({dist[to], to});
        }
      }

      for (auto ptr = alive.begin(); ptr != alive.end(); ptr++) {
        int i = *ptr;
        if (count_edges[cur[1]][i] == 1 && save_edge[cur[1]][i] == forbidden) {
          continue;
        } else {
          if (dist[i] > cur[0] + between[cur[1]][i]) {
            dist[i] = cur[0] + between[cur[1]][i];
            que.push({dist[i], i});
          }
        }
      }
    }
    return dist[perm[0]];
  };

  for (int i = 0; i < n; i++) {
    middleA[i] = middleB[i] = middleC[i] = middleD[i] = -1;
  }
 
  for (int i = 0; i < n; i++) {
    for (auto v : inv[i]) {
      if (d1[perm[0]][v[0]] + (v[1] + 1) == d1[perm[0]][i]) {
        cntA[i]++;
        middleA[i] = v[0];
      }
    }
  }
  for (int i = 0; i < n; i++) {
    for (auto v : adj[i]) {
      if (d1[v[0]][perm[1]] + (v[1] + 1) == d1[i][perm[1]]) {
        cntB[i]++;
        middleB[i] = v[0];
      }
    }
  }
 
  for (int i = 0; i < n; i++) {
    for (auto v : inv[i]) {
      if (d1[perm[1]][v[0]] + (v[1] + 1) == d1[perm[1]][i]) {
        cntC[i]++;
        middleC[i] = v[0];
      }
    }
  }
  for (int i = 0; i < n; i++) {
    for (auto v : adj[i]) {
      if (d1[v[0]][perm[0]] + (v[1] + 1) == d1[i][perm[0]]) {
        cntD[i]++;
        middleD[i] = v[0];
      }
    }
  }

  long long res = inf;
  res = min(res, d2[perm[0]][perm[1]] + d2[perm[1]][perm[0]]);
  for (int i = 0; i < m; i++) {
    int u = edges[i][0];
    int v = edges[i][1];
    int c = edges[i][2];
    int d = edges[i][3];
 
    long long path_from_beg = 0;
 
    bool canA = true;
    bool canB = true;
 
    canA &= (cntA[v] > 1 || middleA[v] != u);
    canB &= (cntB[u] > 1 || middleB[u] != v);
 
    if (canA && canB) {
      path_from_beg = min(d2[perm[0]][perm[1]], d2[perm[0]][v] + d2[u][perm[1]] + c);
    } else {
      swap(perm[0], perm[1]);
      path_from_beg = Update(i, v, u, c);
      swap(perm[0], perm[1]);
    }
 
    canA = true;
    canB = true;
 
    canA &= (cntC[v] > 1 || middleC[v] != u);
    canB &= (cntD[u] > 1 || middleD[u] != v);
 
    long long path_from_end = 0;
    if (canA && canB) {
      path_from_end = min(d2[perm[1]][perm[0]], d2[perm[1]][v] + d2[u][perm[0]] + c);
    } else {
      path_from_end = Update(i, v, u, c);
    }
 
    long long tot = path_from_beg + path_from_end + d;
    res = min(res, tot);
  }
 
  if (res == inf) {
    cout << -1 << '\n';
  } else {
    cout << res << '\n';
  }
  return 0;
}

• Subtask 1: 5 / 5
• Subtask 2: 11 / 11
• Subtask 3: 21 / 21
• Subtask 4: 0 / 63