Submission #827631

#	Time	Username	Problem	Language	Result	Execution time	Memory
827631		taher	Olympic Bus (JOI20_ho_t4)	C++17	100 / 100	115 ms	6928 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;
    }
    vector<bool> u(n);
    dist[perm[1]] = 0;

    for (int i = 0; i < n; i++) {
      int v = -1;
      for (int j = 0; j < n; j++) {
        if (!u[j] && (v == -1 || dist[j] < dist[v])) {
          v = j;
        }
      }

      if (v == -1 || dist[v] == inf) {
        break;
      }
      u[v] = true;

      if (v == source) {
        if (dist[to] > 1LL * dist[v] + cost) {
          dist[to] = dist[v] + cost;
        }
      }

      for (auto edge : adj[v]) {
        if (edge[3] == forbidden) {
          continue;
        }
        if (dist[v] + edge[1] < dist[edge[0]]) {
          dist[edge[0]] = dist[v] + edge[1];
        }
      }
    }
    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[3];
      }
    }
  }
  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[3];
      }
    }
  }
 
  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[3];
      }
    }
  }
  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[3];
      }
    }
  }

  long long res = inf;
  res = min(res, d2[perm[0]][perm[1]] + d2[perm[1]][perm[0]]);

  int counter = 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] != i);
    canB &= (cntB[u] > 1 || middleB[u] != i);

    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] != i);
    canB &= (cntD[u] > 1 || middleD[u] != i);

    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;
}

Compilation message (stderr)

ho_t4.cpp: In function 'int main()':
ho_t4.cpp:167:7: warning: unused variable 'counter' [-Wunused-variable]
  167 |   int counter = 0;
      |       ^~~~~~~

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