Problem p01881 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
// #define LOG(...)
#define FOR(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())
#define RSORT(c) sort((c).rbegin(), (c).rend())
#define CLR(a) memset((a), 0, sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

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

struct UnionFind {
  vector<int> v;
  UnionFind(int n) : v(n) {
    for (int i = 0; i < n; i++)
      v[i] = i;
  }
  int find(int x) { return v[x] == x ? x : v[x] = find(v[x]); }
  void unite(int x, int y) { v[find(x)] = find(y); }
};

int main() {
  int h, w;
  cin >> h >> w;
  vector<string> cells(h);
  vvi able(h, vi(w, 9999));
  REP(i, h)
  cin >> cells[i];
  int sx, sy, gx, gy;
  queue<pair<pii, int>> Qs;

  REP(i, h) {
    REP(j, w) {
      if (cells[i][j] == '@') {
        sx = j;
        sy = i;
      }
      if (cells[i][j] == '%') {
        gx = j;
        gy = i;
      }
      if (cells[i][j] == '$') {
        Qs.push({{i, j}, 0});
        able[i][j] = 0;
      }
      if (cells[i][j] == '#')
        continue;
    }
  }
  while (!Qs.empty()) {
    pair<pii, int> q = Qs.front();
    Qs.pop();
    REP(k, 4) {
      int nx = q.first.second + dx[k];
      int ny = q.first.first + dy[k];
      if (0 <= ny && ny < h && 0 <= nx && nx < w)
        if (cells[ny][nx] != '#')
          if (able[ny][nx] > q.second + 1) {
            able[ny][nx] = q.second + 1;
            Qs.push({{ny, nx}, q.second + 1});
          }
    }
  }
  vvb visited(h, vb(w, false));
  visited[sy][sx] = true;
  queue<pair<pii, int>> Q;
  Q.push({{sy, sx}, 0});
  bool ans = false;
  while (!Q.empty()) {
    pair<pii, int> q = Q.front();
    Q.pop();
    if (q.first.first == gy && q.first.second == gx) {
      ans = true;
      break;
    }
    REP(k, 4) {
      int nx = q.first.second + dx[k];
      int ny = q.first.first + dy[k];
      if (0 <= ny && ny < h && 0 <= nx && nx < w)
        if (cells[ny][nx] != '#' && able[ny][nx] > q.second + 1)
          if (visited[ny][nx] == false) {
            visited[ny][nx] = true;
            Q.push({{ny, nx}, q.second + 1});
          }
    }
  }
  if (ans) {
    cout << "Yes" << endl;
  } else {
    cout << "No" << endl;
  }
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
// #define LOG(...)
#define FOR(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())
#define RSORT(c) sort((c).rbegin(), (c).rend())
#define CLR(a) memset((a), 0, sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

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

struct UnionFind {
  vector<int> v;
  UnionFind(int n) : v(n) {
    for (int i = 0; i < n; i++)
      v[i] = i;
  }
  int find(int x) { return v[x] == x ? x : v[x] = find(v[x]); }
  void unite(int x, int y) { v[find(x)] = find(y); }
};

int main() {
  int h, w;
  cin >> h >> w;
  vector<string> cells(h);
  vvb able(h, vb(w, false));
  REP(i, h)
  cin >> cells[i];
  int sx, sy, gx, gy;
  REP(i, h) {
    REP(j, w) {
      if (cells[i][j] == '@') {
        sx = j;
        sy = i;
      }
      if (cells[i][j] == '%') {
        gx = j;
        gy = i;
      }
      if (cells[i][j] == '#')
        continue;
      vvb visited(h, vb(w, false));
      visited[i][j] = true;
      queue<pair<pii, int>> Q;
      Q.push({{i, j}, 0});
      bool pfast = false;
      bool sfast = false;
      int dis = 9999;
      while (!Q.empty()) {
        pair<pii, int> q = Q.front();
        Q.pop();
        if (q.second > dis)
          break;
        if (cells[q.first.first][q.first.second] == '$') {
          sfast = true;
          break;
        }
        if (pfast)
          continue;
        if (cells[q.first.first][q.first.second] == '@') {
          pfast = true;
          dis = q.second;
          continue;
        }
        REP(k, 4) {
          int nx = q.first.second + dx[k];
          int ny = q.first.first + dy[k];
          if (0 <= ny && ny < h && 0 <= nx && nx < w)
            if (cells[ny][nx] != '#')
              if (visited[ny][nx] == false) {
                visited[ny][nx] = true;
                Q.push({{ny, nx}, q.second + 1});
              }
        }
      }
      if (!sfast && pfast) {
        able[i][j] = true;
      }
    }
  }
  vvb visited(h, vb(w, false));
  visited[sy][sx] = true;
  queue<pii> Q;
  Q.push({sy, sx});
  bool ans = false;
  while (!Q.empty()) {
    pii q = Q.front();
    Q.pop();
    if (q.first == gy && q.second == gx) {
      ans = true;
      break;
    }
    REP(k, 4) {
      int nx = q.second + dx[k];
      int ny = q.first + dy[k];
      if (0 <= ny && ny < h && 0 <= nx && nx < w)
        if (cells[ny][nx] != '#' && able[ny][nx])
          if (visited[ny][nx] == false) {
            visited[ny][nx] = true;
            Q.push({ny, nx});
          }
    }
  }
  if (ans) {
    cout << "Yes" << endl;
  } else {
    cout << "No" << endl;
  }
}