Speedrun C++

Tips and tricks to speedrun C++!

Information

About

A collection of tips and tricks to make writing C++ faster. Really for no reason in particular other than for fun. Some of the tips/tricks here are most certainly not good styling or coding practice but rather something that is more interesting to know, than to actually use.

Styling

These tips/tricks will adhere to being legible so there should be no need to worry about that. For example, if a trick is describing an if statement with no braces, it will not look like this:

if(1==1)return 3;

It will instead look like following:

if (1 == 1) return 3;

Every trick will also have the following by default:

#include <bits/stdc++.h>

using namespace std;

Tips/Tricks

No braces

Some statements and control operators allow you to completely omit braces under certain circumstances.

Examples:

// Before
if (x == y) {
  return true;
}

// After
if (x == y) return true;

// Before
while (x == y) {
  cout << "This is correct";
}

// After
while (x == y) cout << "This is correct";

Initialization

Instead of explicity assigning values to variables when creating them, one can initialize them, saving characters.

Examples:

// Before
vector<string> words = {"This", "is", "correct"};
int index = 0;

// After
vector<string> words{"This", "is", "correct"};
int index{};

// Before
for (int i = 0; i < 64; i++) {
  cout << i;
}

// After
for (int i{}; i < 64; i++) {
  cout << i;
}

// Combination
for (int i{}; i < 64; i++) cout << i;

Type conversion

Sometimes C++ can be annoying, and it requires certain types to be converted. Luckily, there are shortcuts.

Examples:

vector<int> ints = {1, 2, 3};

// Before
for (int i = 0; i < static_cast<int>(ints.size()); i++) {
  cout << ints[i];
}

// After
for (int i = 0; i < (int) ints.size(); i++) {
  cout << ints[i];
}

// Combination
for (int i{}; i < (int) ints.size(); i++) cout << ints[i];

Auto

Don't feel like specifying the type, no problem! In some instances, C++ can infer the type for you.

Examples:

// Before
for (int i = 0; i < 64; i++) {
  cout << i;
}

// After
for (auto i = 0; i < 64; i++) {
  cout << i;
}

// Combination
for (auto i{0}; i < 64; i++) cout << i;