Submission #494350

#	Time	Username	Problem	Language	Result	Execution time	Memory
494350		MilosMilutinovic	Portals (BOI14_portals)	C++14	20 / 100	26 ms	8108 KiB

portals

#include <bits/stdc++.h>

using namespace std;

const int dx[] = {1, -1, 0, 0};
const int dy[] = {0, 0, 1, -1};

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  vector<string> s(n);
  for (int i = 0; i < n; i++) {
    cin >> s[i];
  }
  int sx, sy, cx, cy;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (s[i][j] == 'S') {
        sx = i;
        sy = j;
      }
      if (s[i][j] == 'C') {
        cx = i;
        cy = j;
      }
    }
  }
  vector<vector<pair<int, int>>> up(n, vector<pair<int, int>>(m));
  vector<vector<pair<int, int>>> down(n, vector<pair<int, int>>(m));
  vector<vector<pair<int, int>>> left(n, vector<pair<int, int>>(m));
  vector<vector<pair<int, int>>> right(n, vector<pair<int, int>>(m));
  //up
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (s[i][j] != '#') {
        if (i == 0 || up[i - 1][j] == make_pair(-1, -1)) {
          up[i][j] = make_pair(i, j);
        } else {
          up[i][j] = up[i - 1][j];
        }
      } else {
        up[i][j] = make_pair(-1, -1);
      }
    }
  }
  //down
  for (int i = n - 1; i >= 0; i--) {
    for (int j = 0; j < m; j++) {
      if (s[i][j] != '#') {
        if (i == n - 1 || down[i + 1][j] == make_pair(-1, -1)) {
          down[i][j] = make_pair(i, j);
        } else {
          down[i][j] = down[i + 1][j];
        }
      } else {
        down[i][j] = make_pair(-1, -1);
      }
    }
  }
  //left
  for (int j = 0; j < m; j++) {
    for (int i = 0; i < n; i++) {
      if (s[i][j] != '#') {
        if (j == 0 || left[i][j - 1] == make_pair(-1, -1)) {
          left[i][j] = make_pair(i, j);
        } else {
          left[i][j] = left[i][j - 1];
        }
      } else {
        left[i][j] = make_pair(-1, -1);
      }
    }
  }
  //right
  for (int j = m - 1; j >= 0; j--) {
    for (int i = 0; i < n; i++) {
      if (s[i][j] != '#') {
        if (j == m - 1 || right[i][j + 1] == make_pair(-1, -1)) {
          right[i][j] = make_pair(i, j);
        } else {
          right[i][j] = right[i][j + 1];
        }
      } else {
        right[i][j] = make_pair(-1, -1);
      }
    }
  }
  /*for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      cout << "{" << up[i][j].first << ", " << up[i][j].second << "}" << " ";
    }
    cout << "\n";
  }*/
  vector<vector<vector<tuple<int, int, int>>>> g(n, vector<vector<tuple<int, int, int>>>(m));
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (s[i][j] == '#') continue;
      bool ok = false;
      if (up[i][j] == make_pair(i, j)) {
        ok = true;
      }
      if (down[i][j] == make_pair(i, j)) {
        ok = true;
      }
      if (left[i][j] == make_pair(i, j)) {
        ok = true;
      }
      if (right[i][j] == make_pair(i, j)) {
        ok = true;
      }
      if (ok || false) {
        for (auto nn : {up[i][j], down[i][j], left[i][j], right[i][j]}) {
          if (nn == make_pair(-1, -1)) {
            continue;
          }
          for (auto mm : {up[i][j], down[i][j], left[i][j], right[i][j]}) {
            if (mm == make_pair(-1, -1) || nn == mm) {
              continue;
            }
            int w = abs(i - nn.first) + abs(j - nn.second);
            g[i][j].emplace_back(mm.first, mm.second, w + 1);
          }
        }
      }
      for (int foo = 0; foo < 4; foo++) {
        int ni = i + dx[foo], nj = j + dy[foo];
        if (ni >= 0 && ni < n && nj >= 0 && nj < m && s[ni][nj] != '#') {
          g[i][j].emplace_back(ni, nj, 1);
        }
      }
    }
  }
  set<tuple<int, int, int>> q;
  q.insert({0, sx, sy});
  vector<vector<int>> dist(n, vector<int>(m, 1e9));
  dist[sx][sy] = 0;
  while (!q.empty()) {
    auto it = *q.begin();
    int x = get<1>(it);
    int y = get<2>(it);
    q.erase(q.begin());
    for (auto c : g[x][y]) {
      int w = get<2>(c);
      if (dist[get<0>(c)][get<1>(c)] > dist[x][y] + w) {
        dist[get<0>(c)][get<1>(c)] = dist[x][y] + w;
        q.insert({dist[get<0>(c)][get<1>(c)], get<0>(c), get<1>(c)});
      }
    }
  }
  int ans = dist[cx][cy];
  cout << (ans == 1e9 ? -1 : ans) << '\n';
  return 0;
}

Compilation message (stderr)

portals.cpp: In function 'int main()':
portals.cpp:138:14: warning: 'sy' may be used uninitialized in this function [-Wmaybe-uninitialized]
  138 |   dist[sx][sy] = 0;
      |              ^
portals.cpp:138:10: warning: 'sx' may be used uninitialized in this function [-Wmaybe-uninitialized]
  138 |   dist[sx][sy] = 0;
      |          ^
portals.cpp:152:24: warning: 'cy' may be used uninitialized in this function [-Wmaybe-uninitialized]
  152 |   int ans = dist[cx][cy];
      |                        ^
portals.cpp:152:20: warning: 'cx' may be used uninitialized in this function [-Wmaybe-uninitialized]
  152 |   int ans = dist[cx][cy];
      |                    ^

• Subtask 1: 0 / 11
• Subtask 2: 0 / 20
• Subtask 3: 20 / 20
• Subtask 4: 0 / 19
• Subtask 5: 0 / 30