KEEP IN MIND

1. For Ordered Set, use :

   #include <ext/pb_ds/assoc_container.hpp>
   using namespace __gnu_pbds;
   #define fbo find_by_order
   #define ook order_of_key
    
   template<typename T>
   using ordered_set = tree<T,  null_type,  less<T>,  rb_tree_tag,  tree_order_statistics_node_update>;
   
   // used as ordered_set<int>  S; 
   // S.insert(123);
   // use 'less_equal<T>' to support duplicates
   // S.ook(x) : number of elements in S strictly less than 'x'
   // S.size() - S.ook(x) : number of elements in S >= x
   // *S.fbo(i) : i'th element in S (0 - based indexing)

2. For random number generator: (add these two lines on top, range is [a, b] )

std::mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define uid(a, b) uniform_int_distribution<int>(a, b)(rng)

3. Priority Queue Initialisation :

   template<class T> using pq = priority_queue<T>;
   template<class T> using pqg = priority_queue<T, vector<T>, greater<T>>;

4. For accurate square root use : (credits : errichto)

   long long x = sqrtl(a) + 2;
   while (x * x > a) x--;

5. Grid cell (i, j) is uniquely mapped to (i + j * n) OR (j + i * m). Print the values.

6. Never use endl, unless in interactive problems. Always make a habit of using '\n' for new line.

7. Rather than clearing globals before each test case, you can also do:

   // GLOBAL DECLARATION WITHOUT SIZE
   vector<vector<int>> adj;
   vector<vector<int>> up; 
   vector<int> tin, tout;
   vector<int> depth;
   
   // INSIDE MAIN ASSIGN SIZE:
   adj = vector<vector<int>> (n + 5);
   up = vector<vector<int>> (n + 5, vector<int>(24));
   tin = vector<int> (n + 5);
   tout = vector<int> (n + 5);
   depth = vector<int> (n + 5);

8. ckmax and ckmin . It returns TRUE if assignment happens else FALSE.

   template<class T> bool ckmin(T& a, const T& b) { return a > b ? a = b, 1 : 0; }
   template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }