c++ debugging template

Topics

• c++ STL

I use the following minimal template for solving coding problems. It has the debug(...) macro that allows me to print out vectors, maps, etc like python print(...) (pretty useful imo!). This template might change in future as I add other templates for common ds and algos.

#include <bits/stdc++.h>
using namespace std;
 
// Type Aliases
using ll = long long;
using vi = vector<int>;
using vll = vector<ll>;
using vvi = vector<vector<int>>;
using vvll = vector<vector<ll>>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vpii = vector<pair<int, int>>;
using vpll = vector<pair<ll, ll>>;
using vvpii = vector<vector<pair<int, int>>>;
using vvpll = vector<vector<pair<ll, ll>>>;
 
// Macros
#define all(x) x.begin(), x.end()
#define pb push_back
#define mp make_pair
 
// Debugging Setup - Enabled when compiling with -DDEBUG
#ifdef DEBUG
// Helper to check if a type is iterable (has begin() and end())
template <typename T, typename = void> struct is_iterable : false_type {};
template <typename T>
struct is_iterable<T, void_t<decltype(begin(declval<T>())),
                                  decltype(end(declval<T>()))>>
    : true_type {};
 
// Overload for pair
template <typename A, typename B>
ostream &operator<<(ostream &os, const pair<A, B> &p) {
  return os << '(' << p.first << ", " << p.second << ')';
}
 
// Overload for iterable types (vector, set, map, etc.), except string
// This works recursively for nested containers (e.g., vector<vector<int>>,
// vector<vector<pair<int,int>>>)
template <typename T>
typename enable_if<is_iterable<T>::value && !is_same<T, string>::value,
                   ostream &>::type
operator<<(ostream &os, const T &v) {
  os << "[";
  bool first = true;
  for (const auto &x : v) {
    if (!first)
      os << ", ";
    os << x; // Recursively calls the appropriate operator<< for type of x
    first = false;
  }
  os << "]";
  return os;
}
 
// Base case for debug_out recursion (handles empty debug() call)
void debug_out() { cerr << "\n"; }
 
// Recursive variadic template for printing multiple arguments
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << H; // Print the current argument
  if (sizeof...(T) > 0)
    cerr << " ";   // Add space only if more arguments follow
  debug_out(T...); // Recurse for remaining arguments
}
 
// The debug macro: prints variable names and values
// Example: debug(x, y, vec); -> prints "[x, y, vec] = value_of_x value_of_y
// [elements_of_vec]"
#define debug(...)                                                             \
  cerr << "[" << #__VA_ARGS__ << "] = ";                                       \
  debug_out(__VA_ARGS__)
#else
// If DEBUG is not defined, debug calls do nothing
#define debug(...)
#endif
 
void solve() {
 
}
 
signed main() {
  // Fast I/O
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
 
  int t = 1;
  cin >> t; // comment for single test case
  while(t--) {
    solve();
  }
 
  return 0;
}

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