Problem p01453 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
/*
 */

using namespace std;

typedef pair<long long int, pair<long long int, long long int>> one;

#define mod 1000000007LL
int main() {
  long long int W, H;
  cin >> W >> H;
  vector<string> D(H);
  long long int counttile = 0;
  pair<long long int, long long int> start, goal;
  vector<pair<long long int, long long int>> warp;
  vector<vector<pair<long long int, long long int>>> len(
      H, vector<pair<long long int, long long int>>(
             W, make_pair(LLONG_MAX / 500 / 500 / 500,
                          LLONG_MAX / 500 / 500 / 500)));
  vector<pair<long long int, long long int>> tile;
  for (size_t i = 0; i < H; i++) {
    cin >> D[i];
    for (size_t j = 0; j < D[i].length(); j++) {
      if (D[i][j] == 's') {
        D[i][j] = '.';
        tile.push_back(make_pair(i, j));
        start.first = i;
        start.second = j;
        counttile++;
      } else if (D[i][j] == 'g') {
        goal.first = i;
        goal.second = j;
      } else if (D[i][j] == '*') {
        warp.push_back(make_pair(i, j));
      } else if (D[i][j] == '.') {
        counttile++;
        tile.push_back(make_pair(i, j));
      }
    }
  }
  int dx[] = {0, 1, 0, -1};
  int dy[] = {1, 0, -1, 0};
  {
    priority_queue<one, vector<one>, greater<one>> que;
    que.push(make_pair(0, goal));
    while (que.size()) {
      auto now = que.top();
      que.pop();
      for (size_t i = 0; i < 4; i++) {
        auto next = now;
        next.first++;
        next.second.first += dx[i];
        next.second.second += dy[i];
        if (0 <= next.second.first && next.second.first < H &&
            0 <= next.second.second && next.second.second < W) {
          if (D[next.second.first][next.second.second] == '.') {
            if (len[next.second.first][next.second.second].first > next.first) {
              len[next.second.first][next.second.second].first = next.first;
              que.push(next);
            }
          }
        }
      }
    }
  }
  queue<one> que;
  for (auto x : warp) {
    que.push(make_pair(0, x));
  }
  while (que.size()) {
    auto now = que.front();
    que.pop();
    if (len[now.second.first][now.second.second].second < now.first) {
      continue;
    }
    for (size_t i = 0; i < 4; i++) {
      auto next = now;
      next.first++;
      next.second.first += dx[i];
      next.second.second += dy[i];
      if (0 <= next.second.first && next.second.first < H &&
          0 <= next.second.second && next.second.second < W) {
        if (D[next.second.first][next.second.second] == '.') {
          if (len[next.second.first][next.second.second].second > next.first) {
            len[next.second.first][next.second.second].second = next.first;
            que.push(next);
          }
        }
      }
    }
  }

  long double maxExpectedValue = W * H * W * H, minExpectedValue = 0;
  for (size_t indexindex = 0; indexindex < 16300; indexindex++) {
    long double midExpectedValue = (maxExpectedValue + minExpectedValue) / 2.L;
    // cout << fixed << setprecision( 20 ) << maxExpectedValue << " " <<
    // minExpectedValue << endl;
    long double countExpectedValue = 0;
    for (auto point : tile) {
      long long int i = point.first, j = point.second;
      countExpectedValue +=
          min(1.L * len[i][j].first, len[i][j].second + midExpectedValue);
    }
    countExpectedValue /= counttile;
    if (midExpectedValue < countExpectedValue) {
      minExpectedValue = midExpectedValue;
    } else {
      maxExpectedValue = midExpectedValue;
    }
  }
  // cout << fixed << setprecision( 20 ) << 1.L*
  // len[start.first][start.second].first << " " <<
  // len[start.first][start.second].second + maxExpectedValue << endl;
  cout << fixed << setprecision(20)
       << min(1.L * len[start.first][start.second].first,
              len[start.first][start.second].second + maxExpectedValue)
       << endl;
}

Fixed submission:
#include <bits/stdc++.h>
/*
 */

using namespace std;

typedef pair<long long int, pair<long long int, long long int>> one;

#define mod 1000000007LL
int main() {
  long long int W, H;
  cin >> W >> H;
  vector<string> D(H);
  long long int counttile = 0;
  pair<long long int, long long int> start, goal;
  vector<pair<long long int, long long int>> warp;
  vector<vector<pair<long long int, long long int>>> len(
      H, vector<pair<long long int, long long int>>(
             W, make_pair(LLONG_MAX / 500 / 500 / 500,
                          LLONG_MAX / 500 / 500 / 500)));
  vector<pair<long long int, long long int>> tile;
  for (size_t i = 0; i < H; i++) {
    cin >> D[i];
    for (size_t j = 0; j < D[i].length(); j++) {
      if (D[i][j] == 's') {
        D[i][j] = '.';
        tile.push_back(make_pair(i, j));
        start.first = i;
        start.second = j;
        counttile++;
      } else if (D[i][j] == 'g') {
        goal.first = i;
        goal.second = j;
      } else if (D[i][j] == '*') {
        warp.push_back(make_pair(i, j));
      } else if (D[i][j] == '.') {
        counttile++;
        tile.push_back(make_pair(i, j));
      }
    }
  }
  int dx[] = {0, 1, 0, -1};
  int dy[] = {1, 0, -1, 0};
  {
    priority_queue<one, vector<one>, greater<one>> que;
    que.push(make_pair(0, goal));
    while (que.size()) {
      auto now = que.top();
      que.pop();
      for (size_t i = 0; i < 4; i++) {
        auto next = now;
        next.first++;
        next.second.first += dx[i];
        next.second.second += dy[i];
        if (0 <= next.second.first && next.second.first < H &&
            0 <= next.second.second && next.second.second < W) {
          if (D[next.second.first][next.second.second] == '.') {
            if (len[next.second.first][next.second.second].first > next.first) {
              len[next.second.first][next.second.second].first = next.first;
              que.push(next);
            }
          }
        }
      }
    }
  }
  queue<one> que;
  for (auto x : warp) {
    que.push(make_pair(0, x));
  }
  while (que.size()) {
    auto now = que.front();
    que.pop();
    if (len[now.second.first][now.second.second].second < now.first) {
      continue;
    }
    for (size_t i = 0; i < 4; i++) {
      auto next = now;
      next.first++;
      next.second.first += dx[i];
      next.second.second += dy[i];
      if (0 <= next.second.first && next.second.first < H &&
          0 <= next.second.second && next.second.second < W) {
        if (D[next.second.first][next.second.second] == '.') {
          if (len[next.second.first][next.second.second].second > next.first) {
            len[next.second.first][next.second.second].second = next.first;
            que.push(next);
          }
        }
      }
    }
  }

  long double maxExpectedValue = W * H * 100000, minExpectedValue = 0;
  for (size_t indexindex = 0; indexindex < 16300; indexindex++) {
    long double midExpectedValue = (maxExpectedValue + minExpectedValue) / 2.L;
    // cout << fixed << setprecision( 20 ) << maxExpectedValue << " " <<
    // minExpectedValue << endl;
    long double countExpectedValue = 0;
    for (auto point : tile) {
      long long int i = point.first, j = point.second;
      countExpectedValue +=
          min(1.L * len[i][j].first, len[i][j].second + midExpectedValue);
    }
    countExpectedValue /= counttile;
    if (midExpectedValue < countExpectedValue) {
      minExpectedValue = midExpectedValue;
    } else {
      maxExpectedValue = midExpectedValue;
    }
  }
  // cout << fixed << setprecision( 20 ) << 1.L*
  // len[start.first][start.second].first << " " <<
  // len[start.first][start.second].second + maxExpectedValue << endl;
  cout << fixed << setprecision(20)
       << min(1.L * len[start.first][start.second].first,
              len[start.first][start.second].second + maxExpectedValue)
       << endl;
}