oj.uz

Submission #784840

# Submission time Handle Problem Language Result Execution time Memory
784840 2023-07-16T15:13:27 Z jakobrs Tracks in the Snow (BOI13_tracks) C++17
100 / 100
 1871 ms 1048576 KB 
#include <iostream>
#include <set>
#include <vector>

using i32 = int32_t;

struct UnionFind {
  std::vector<i32> parent;

  explicit UnionFind(size_t sz) : parent(sz, -1) {}

  i32 find(i32 u) {
    if (parent[u] < 0)
      return u;
    else
      return parent[u] = find(parent[u]);
  }

  bool unite(i32 u, i32 v) {
    u = find(u);
    v = find(v);

    if (u == v) {
      return false;
    } else {
      if (-parent[u] < -parent[v])
        std::swap(u, v);

      parent[u] += parent[v];
      parent[v] = u;

      return false;
    }
  }
};

int main() {
  std::cin.tie(nullptr)->sync_with_stdio(false);

  i32 h, w;
  std::cin >> h >> w;

  std::vector<std::string> grid(h);
  for (i32 i = 0; i < h; i++)
    std::cin >> grid[i];

  UnionFind dsu(h * w);

  i32 idx = 0;
  for (i32 r = 0; r < h; r++) {
    const auto &row = grid[r];
    for (i32 c = 0; c < w; c++, idx++) {
      if (c + 1 < w && grid[r][c] == grid[r][c + 1]) {
        dsu.unite(idx, idx + 1);
      }
      if (r + 1 < h && grid[r][c] == grid[r + 1][c]) {
        dsu.unite(idx, idx + w);
      }
    }
  }

  std::vector<std::set<i32>> adj(h * w);

  auto adge = [&](i32 u, i32 v) {
    adj[dsu.find(u)].insert(dsu.find(v));
    adj[dsu.find(v)].insert(dsu.find(u));
  };

  idx = 0;
  for (i32 r = 0; r < h; r++) {
    const auto &row = grid[r];
    for (i32 c = 0; c < w; c++, idx++) {
      if (row[c] == '.') continue;
      char op = row[c] == 'F' ? 'R' : 'F';

      if (c + 1 < w && grid[r][c + 1] == op) {
        adge(idx, idx + 1);
      }
      if (r + 1 < h && grid[r + 1][c] == op) {
        adge(idx, idx + w);
      }
    }
  }

  std::vector<i32> next;
  std::vector<i32> front { dsu.find(0) };
  std::vector<bool> visited(h * w, false);
  visited[0] = true;
  int t;
  for (t = 0; !front.empty(); t++) {
    for (int x : front) {
      for (int neighbour : adj[x]) {
        if (!visited[neighbour]) {
          visited[neighbour] = true;
          next.push_back(neighbour);
        }
      }
    }

    std::swap(next, front);
    next.clear();
  }

  std::cout << t;
}

Compilation message

tracks.cpp: In function 'int main()':
tracks.cpp:51:17: warning: unused variable 'row' [-Wunused-variable]
   51 |     const auto &row = grid[r];
      |                 ^~~

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 45 ms 18036 KB Output is correct
2 Correct 0 ms 340 KB Output is correct
3 Correct 1 ms 468 KB Output is correct
4 Correct 10 ms 8532 KB Output is correct
5 Correct 5 ms 5460 KB Output is correct
6 Correct 0 ms 340 KB Output is correct
7 Correct 1 ms 468 KB Output is correct
8 Correct 1 ms 596 KB Output is correct
9 Correct 1 ms 852 KB Output is correct
10 Correct 5 ms 4564 KB Output is correct
11 Correct 3 ms 2516 KB Output is correct
12 Correct 12 ms 6740 KB Output is correct
13 Correct 6 ms 5460 KB Output is correct
14 Correct 5 ms 5544 KB Output is correct
15 Correct 29 ms 17956 KB Output is correct
16 Correct 38 ms 18000 KB Output is correct
17 Correct 23 ms 16944 KB Output is correct
18 Correct 10 ms 8616 KB Output is correct

Subtask #2
70.0 / 70.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 3412 KB Output is correct
2 Correct 156 ms 103608 KB Output is correct
3 Correct 1104 ms 996316 KB Output is correct
4 Correct 257 ms 222016 KB Output is correct
5 Correct 910 ms 891044 KB Output is correct
6 Correct 1282 ms 889040 KB Output is correct
7 Correct 4 ms 3028 KB Output is correct
8 Correct 3 ms 3412 KB Output is correct
9 Correct 5 ms 4052 KB Output is correct
10 Correct 2 ms 2132 KB Output is correct
11 Correct 2 ms 3028 KB Output is correct
12 Correct 2 ms 2516 KB Output is correct
13 Correct 138 ms 103700 KB Output is correct
14 Correct 83 ms 60112 KB Output is correct
15 Correct 104 ms 65608 KB Output is correct
16 Correct 67 ms 44208 KB Output is correct
17 Correct 355 ms 268292 KB Output is correct
18 Correct 431 ms 260352 KB Output is correct
19 Correct 264 ms 221900 KB Output is correct
20 Correct 212 ms 213524 KB Output is correct
21 Correct 569 ms 574536 KB Output is correct
22 Correct 880 ms 891240 KB Output is correct
23 Correct 686 ms 514044 KB Output is correct
24 Correct 593 ms 614476 KB Output is correct
25 Correct 1603 ms 1048576 KB Output is correct
26 Correct 514 ms 638532 KB Output is correct
27 Correct 574 ms 835776 KB Output is correct
28 Correct 1350 ms 889068 KB Output is correct
29 Correct 1165 ms 866252 KB Output is correct
30 Correct 960 ms 839664 KB Output is correct
31 Correct 1871 ms 750664 KB Output is correct
32 Correct 633 ms 847460 KB Output is correct