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C++ Control Statements

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C++ Functions

C++ Call by Value C++ Call by Reference C++ Recursion Function C++ Inline function C++ Friend function

C++ Arrays

Single dimension array Two dimension array

C++ Strings

C++ Strings

C++ Inheritance

C++ Inheritance Single level Inheritance Multilevel Inheritance Multiple Inheritance Hierarchical Inheritance Hybrid Inheritance

C++ Polymorphism

C++ Polymorphism C++ Overloading C++ Overriding C++ Virtual Function

C++ Pointers

C++ Pointers C++ this pointer

C++ Exception Handling

C++ Exception Handling

C++ Constructors

C++ Constructors Default Constructor Parameterize Constructor Copy constructor Constructor Overloading Destructor

C++ File Handling

C++ File Handling C++ Writing to file C++ Reading file C++ Close file

Miscellaneous

C Vs C++ C++ Comments C++ Data Abstraction C++ Identifier C++ Memory Management C++ Storage Classes C++ Void Pointer C++ Array To Function C++ Expressions C++ Features C++ Interfaces C++ Encapsulation std::min in C++ External merge sort in C++ Remove duplicates from sorted array in C++ Precision of floating point numbers Using these functions floor(), ceil(), trunc(), round() and setprecision() in C++ C++ References C++ Friend Functions C++ Mutable keyword Unary Operators in C++ Initialize Array of objects with parameterized constructors in C++ Differences between #define & const in C/C++ C++ Program to Implement Shell Sort C++ Program to Implement Merge Sort Storage Classes in C Vector resize() in C++ Passing by Reference Vs. Passing by the pointer in C++ Free vs delete() in C++ goto statement in C and C++ C++ program to read string using cin.getline() C++ String Concatenation Heap Sort in C++ Swap numbers in C++ Input Iterators in C++ Fibonacci Series in C++ C ++ Program: Alphabet Triangle and Number Triangle C++ Program: Matrix Multiplication C++ Program to Print Fibonacci Triangle Stack in C++ Maps in C++ Queue in C++ C++ Bitset C++ Algorithms Priority Queue in C++ C++ Multimap C++ Deque Function Pointer in C++ Sizeof() Operators in C++ C++ array of Pointers free() Vs delete in C Timsort Implementation Using C++ CPP Templates C++ Aggregation C++ Enumeration C++ Math Functions C++ Object Class C++ Queue Initialize Vector in C++ Vector in C++ C++ STL Components Function overloading in C++ C++ Maximum Index Problem C++ find missing in the second array C++ Program to find the product array puzzle C++ Program To Find Largest Subarray With 0 Sum C++ Program To Move All Zeros To The End Of The Array C++ Program 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in C++ Factorial Program in C++ Function in C++ Hexadecimal to Decimal in C++ Octal to Decimal in C++ Reverse a Number in C++ Structure Vs Class in C++ C++ Forward Iterators C++ Output Iterators C++ Prime number program Char Array to String in C++ Constructor Overloading in C++ Default arguments in C++ Different Ways to Compare Strings in C++ Dynamic Binding in C++ Program to convert infix to postfix expression in C++ SET Data Structure in C++ Upcasting and Downcasting in C++ Reverse an Array in C++ Fast Input and Output in C++ Delete Operator in C++ Copy elision in C++ C++ Date and Time C++ Bitwise XOR Operator Array of sets in C++ Binary Operator Overloading in C++ Binary Search in C++ Implementing the sets without C++ STL containers Scope Resolution Operator in C++ Smart pointers in C++ Types of polymorphism in C++ Exception Handling in C++ vs Java Const Keyword in C++ Type Casting in C++ Static keyword in C++ vs Java Inheritance in C++ vs Java How to concatenate two strings in C++ Programs to Print Pyramid Patterns in C++ swap() function in C++ Structure of C++ Program Stringstream in C++ and its applications rand() and srand() in C / C++ C++ Ternary Operator C++ Scope of Variables While Loop Examples in C++ Star pattern in C++ using For Loops For Loop Examples in C++ Do-While Loop Examples in C++ Top 5 IDEs for C++ That You Should Try Once Assertions in C/C++ C++ Convert Int to String Continue in C++ While loop Diamond Pattern in C++ using For Loop How to Reverse a String in C++ using Do-While Loop How to Reverse a String in C++ using For Loop How to Reverse a String in C++ using While Loop Infinite loop in C++ Loops in C++ Returning Multiple Values from a Function using Tuple and Pair in C++ wcscpy(), wcslen(), wcscmp() Functions in C++ Auto keyword in C++ C++ 11 vs C++ 14 vs C++ 17 C++ STL (Standard Template Library) Differences Between C Structures and C++ Structures Divide by Zero Exception in C++ Dynamic Constructor in C++ Dynamic Memory Allocation in C++ Find the Size of Array in C/C++ without using sizeof() function Floating Point Operations and Associativity in C, C++ and Java Hello World Program in C++ How to create a table in C++ How to Setup Environment for C++ Programming on Mac Implementation of a Falling Matrix in C++ Message Passing in C++ Pointer to Object in C++ Templates in C++ vs Generics in Java Ways to Copy a Vector in C++ What does Buffer Flush mean in C++ sort() function in C++ Structure Sorting (By Multiple Rules) in C++ Similarities between C++ and Java std::distance in C++ Array program in C++ C++ Tricks for Competitive Programming Desired Capabilities in Selenium Web Driver in C++ Socket Programming in C++ Template Specialization in C++ Classes and Objects in C++ Convex hull Algorithm in C++ DES in C++ C++ vardiac() function Difference between Two Sets in C++ Difference between Exit and Return Structured Binding in C++ Differences between Local and Global Variable Bitwise Operator vs Logical Operator Difference between OOP and POP in C++ Fork in C++ Functors in C++ How to call a void function in C++ How to create a directory or folder in C/C++ How to create a library in C++ How to create a stack in C++ How to create the Processes with Fork in C++ How to Handle Divide by Zero Exception in C++ Lambda Expression in C++ Pattern programs in C++ Roadmap to C++ Programming Substring in C++ Virtual base class in C++ Bits stdc++.h in C++ Top 14 Best Free C++ IDE (Editor & Compiler) for Windows in 2022 Bitmasking in C++ Auto Keyword in C++ Features of OOPS in C++ Hospital Management Project in C++ How to Declare Unordered Sets in C++ How to Sort an Array in C++ Include Guards in C++ Iostream in C++ Method overriding in C++ How to run program in turbo c++ How to Use Getline in C++ Leap Year Program in C++ Naming Convention in C++ New Operator in C++ Nullptr in C++ Object Slicing in C++ Principles of Object-Oriented Programming in C++ Processing strings using std string stream in C++ Pure Virtual Function in C++ With Example Program Random Number Generator in C++ Singleton Design Pattern in C++ Size_t Data Type in C++ Skyline Problem in C++ System() function in C++ Web Development in C++ Data Hiding in C++ Difference between exit() and _Exit() in C++ Hashing in C++ Object in C++ Sum of all Elements between k1’th and k2’th Smallest Elements Virtual class in C++ Vector Size in C++ Top best IDEs for C/C++ Developers in 2022 Tensorflow in C++ Sliding Window Technique in C++ Reverse String Word-Wise in C++ Returning a Function Pointer from a Function in C/C++ RTTI in C++ Pthreads or POSIX Threads in C++ Reserved Keywords in C++ Passing a Vector to a function in C++ 10 Best C and C++ Books for Beginners & Advanced Programmers Add two numbers represented by two arrays in C++ Array of Object in C++ C++ Program For FCFS Containership in C++ Counting Frequencies of Array Elements in C++ Decltype type Specifier in C++ Dynamic _Cast in C++ Difference between int main() and int main(void) in C/C++ Depth First Search Program to Traverse a Graph in C++ Features and Use Of Pointers in C/C++ Fread Function in C++ Programming Fscanf Function in The C++ Functions in C++ With Types and Examples Gmtime Function in C/C++ How is Multiset Implemented in C++ How to Build a Program in C++ How to Declare a 2d Array Dynamically in C++ inheritance Program in C++ int Max and int Min in C/C++ is It Fine to Write Void Main Or Main in C/C++ How to create a button in C++ abs() function in C++ Compile Time Polymorphism in C++ Division in C++ Factorial of a Number in C++ using while Loop Multiset in C++ 4 Pillars of OOPs Approach in C++ Backtracking Time Complexity in C++ C++ Global Variable C++ Pipe Tutorial Observer Design Pattern in C++ Private Inheritance in C++ Pthread in C++ Parameters SDL library in C++ with Examples Pointers in C++ Abstract Factory Design Pattern in C++ Ascending order in C++ How the value is passed in C++ Call by Pointer in C++ Constexpr in C++ Deadlock in C++ Design Patterns in C++ Factory Method for Designing Pattern in C++ How to calculate size of string in C++ Name Mangling and extern in C++ Preventing Object Copy in C++ Program that produces different results in C and C++ Quick Sort in C++ Single Handling in C++ Type difference of Character literals in C VS C++ Use of Inheritance in C++ User-defined literals in C++ Vector methods in C++ Void * in C and C++ Zombie and Orphan Process in C++ Isprint() in C++ List and Vector in C++ List iterators in C++ Merging Two Vectors in C++ Sleep function in C++ Stoi function in C++ String erase() in C++ String Trim in C++ When should we write own Assignment operator in C++ C++ tcp client server example C++ tcp server example Early Binding and Late Binding in C++ Factory Design Pattern in C++ Fisher-Yates shuffle algorithm in C++ For Auto in C++ Group anagrams in C++ How to convert binary string to int in C++ How to convert string to float in C++ How to remove space from string in C++ How to use pair in C++ How to use the string find() in C++ Dynamic Casting in C++ 2D Vector Initialization in C++ C++ GUI Visual Studio C++ IPC C++ Macro Function Example C++ Permutation Overloading Stream Insertion in C++ Overloading array Index operator in C++ Operators that cannot be overloaded in C++ Operator overloading in C++ isprint() function in c++ Is_trivial function in C++ Is assignment operator Inherited in C++ div() function in C++ Default Assignment Operator and References in C++ Copy Constructor vs Assignment Operator in C++ Conversion Operator in C++ Array sum in C++ STL C++ Define Macro C++ Design C++ Factory Pattern TCP Client Server Example in C++ Convert String to Uppercase in C++ exit() and _Exit() in C and C++ Initializer list in C++ Iterator invalidation in C++ Lower bound in C++ Modulus of Two float numbers or double number Pass by value in C++ Set insert function in C++ Std partition_point in C++ Unary Operator Overloading in C++ Using Default Arguments with Virtual Functions Virtual Functions and Runtime Polymorphism What is endl in C++ What is Unary Operator Overloading in C++ Which operators cannot be overloaded in C++ C++ Program to Divide the String Into N equal Parts Gray Code to Binary Code in C++ How to get the value of pi in C++ Multimap value_comp() function in C++ Vector of Vectors in C++ Naïve Bayes Algorithm in C++ Minimum Cost Path Problem in C++ 10 C++ Programming Tricks You Should Know btowc() function in C++ forward_list::cend() in C++ Unordered_multimap max_load_factor() function in C++ Cpp_int in c++ Dynamic Objects in C++ FLOCK() FUNCTION IN C++ Generate Random Double Numbers in C++ How to Assign Infinity to a Number in C++ Jump statements in C++ Multipath inheritance in C++ Out of Range Exception in C++ Size of Class in C++ Size of string in C++ std::binary_negate in c++ Thread_local in C++ Tokenizing a String in C++ Ancestors of a Node in Binary Search Tree C++ program for Double to String Conversion C++ Program to Demonstrate Use of Formatting Flags on Float Output Clamp in C++ K-Dimensional Tree in C++ Mutable Lambda in C++ Power Set in C++ Program to Find Sum of Geometric Progression Std::Back_inserter in C++ Strpbrk() function in C++ Size of int in C++ TYPES OF MANIPULATORS IN C++ Double colon in C++ How to sort vector in C++ How to use Setprecision in C++ How to write a Vector in C++ Insertion in Splay Tree in C++ Merge Sort Algorithm in C++ Printing a Character using ASCII value in C++ Regex in C++ Size of Data Types in C++ Sqrtf() function in C++ Static Casting in C++ Using Range in Switch Case in C++ wcstoimax() and wcstoumax() function in C++ What is float in C++ What is the Diamond Problem in C++ Best way to learn C++ ios setstate() function in C++ Nested Namespace in C++ Single Inheritance in C++ std::fixed, std::scientific, std::hexfloat, std::defaultfloat in C++ StringStream in C++ for Decimal to Hexadecimal and back The OFFSETOF() macro in C++ Difference between std::next and std::advance in C++ Hiding of all overloaded methods with same name in base class in C++ C++ program to concatenate two strings using operator overloading Difference between array::fill() and array::swap() in C++ Difference between Friend Function and Virtual Function in C++ Semaphores in C++ Seekg in C++ UDP server- client implementattion in C++ What is long long in C++ CSV file management using C++ Toggle bits of a number except first and last bits in C++ Trailing Return Type C++ 11 Binary search implementation in C++ Different Versions of C++ What is Cascading in C++ Background Colour in C++ BOOL DATATYPE IN C++ BIT VECTORS IN C++ Literals in C++ Application of pointer in C++ Index with minimum sum of prefix and suffix sums in an array in C++ Maximum sum Bi-tonic sub-sequence in C++ std::optional in C++ C/C++ program for triangular matchstick number COUT COMMAND IN C++ LANGUAGE Adjacency matrix program in C++ language Difference between Null String and Empty String in C++ Character data type in c++ Constructors in Inheritance C++ Comma Operator Overloading in C++ Structure and Class in C++ Template Definition in C++ Tree Data Structure in C++ Typename in C++ C++ program to implement the bin packing algorithm How to merge multiple std::sets into a single std::set in C++? Stack Clear C++ C++ Friend Class Seekg in C++ Semaphores in C++ C++ Exceptions Difference Between C and C++ Double-linked list program in C++ Color Code in C++ CRC Program in C++ Anti-Clockwise spiral traversal of a binary tree in C++ Advantages of OOP in C++ Cryptarithmetic Puzzle in C++ Angular sweep algorithm in C++

C++ Tricks for Competitive Programming

If you are interested in Computer science or Information technology, you must have heard about competitive programming. Competitive programming is a way to improve your problem-solving skills. There are various competitive programming platforms available nowadays. In competitive programming, you have to solve problems on your merit. But it is also true that in every place, there are some tricks used to solve problems in a short time. These tricks provide some features that take less time to solve problems. So, if you know the tricks, you will surely get the advantage. In this article, we will discuss some tricks which are available in the C++ language, especially in C++ 11.

1. Include all standard libraries

We use many standard libraries to insert different things in our code. These libraries are as follows:

#include <iostream>

#include <algorithm>

#include <vector>

#include <string>

#include <stack>

#include <set>

#include <queue>

#include <map>

Instead of including each standard library individually, use #include <bits/stdc++.h> to include all of them in your project. This would be particularly helpful in a programming contest where speed is of concern. There are numerous header files in <bits/stdc++.h> that you might not need for your project. The time required for compilation may increase as a result.

2. Using range-based for loop

C++ 11 runs for loop across a number of values. It is used as a more readable alternative to the classic for loop that operates over a range of values, such as all of the container's elements. If you wish to iterate sequentially from beginning to end, this C++11 feature is the best. Below the given code is an example of the implementation of the above-said feature.

#include <iostream>
#include <map>
#include <vector>
int main()
{
	std::vector<int> v = { 0, 1, 2, 3, 4, 5 };
	for (auto i : v)
		std::cout << i << ' ';


	std::cout << '\n';
	for (int n : { 0, 1, 2, 3, 4, 5 })
		std::cout << n << ' ';


	std::cout << '\n';
	int a[] = { 0, 1, 2, 3, 4, 5 };
	for (int n : a)
		std::cout << n << ' ';


	std::cout << '\n';
	for (int n : a)
		std::cout << "hello world" << ' ';


	std::cout << '\n';
	std::string str = "earth";
	for (char c : str)
		std::cout << c << ' ';


	std::cout << '\n';
	std::map<int, int> MAP(
		{ { 1, 1 }, { 2, 2 }, { 3, 3 } });
	for (auto i : MAP)
		std::cout << '{' << i.first << ", " << i.second
				<< "}\n";
}

Output:

C++ Tricks for Competitive Programming

3. Use auto to omit the data type of a variable

The auto keyword indicates that the type of the variable being defined will be deduced automatically from its initialiser. When it comes to functions, a return type expression will be used at runtime to determine whether the return type is auto. When generating iterators for containers, it is a good idea to utilise auto to minimise lengthy initialisations. If a variable containing the auto keyword is not initialised at the time of declaration, a compile time error will be occurred. Below the given code is an example of the implementation of the above-said feature.

//First program:
#include <bits/stdc++.h>
using namespace std;


int main()
{
	auto x = 4;
	auto y = 3.37;
	auto ptr = &x;
             auto a = 'a';
            auto t = true;
	cout << typeid(x).name() << endl
		<< typeid(y).name() << endl
		<< typeid(ptr).name() << endl;


	return 0;
}


//Second program:
#include <bits/stdc++.h>
using namespace std;


int main()
{
	set<string> st;
	st.insert({ "world", "is", "very", "nice" });
	for (auto it = st.begin(); it != st.end(); it++)
		cout << *it << " ";


	return 0;
}

Output:

C++ Tricks for Competitive Programming

4. Checking if the number is even or odd without using the % operator

Although utilising the % operator is still preferable, this method can still be useful in certain circumstances (with large numbers). The goal is to determine whether or not the number's final bit is set. The number is odd if the last bit is set; otherwise even. We know that in bitwise and operation, the answer will be 1 if and only if both the bits are 1. We use this technique only. Below the given code is an example of the implementation of the above-said features.

Code using % operator:

#include <iostream>
using namespace std;
bool isEven(int n)
{
	If ( n%2 == 0 )
	return true;
	else
	return false;
}
int main()
{
	int n = 101;
	isEven(n)
	? cout << "Even"
	: cout << "Odd";
	return 0;
}

Output:

C++ Tricks for Competitive Programming

Code using & operator:

#include <iostream>
using namespace std;
bool isEven(int n)
{
	return (!(n & 1));
}
int main()
{
	int n = 101;
	isEven(n)
	? cout << "Even"
	: cout << "Odd";
	return 0;
}

Output:

C++ Tricks for Competitive Programming

5. Use of ternary operator instead of if else statement

It is often seen that we have to use conditional statement in many places. We mainly use if else statements to apply conditions. We use this very frequently because it is easy to use this type of conditional statement in our code. But just think about competitive programming. You have to increase your speed in that situation. So for every conditional case, if you use if-else statement then it will take time to complete your code. But ternary operator can be use as the replacement of if else statement. See the following code to understand how if else statements increase your time and decrease the speed.

Code using if-else statement:

#include <iostream>
using namespace std;
int fun(int n)
{
	If ( n > 100 )
	{
	return 1;
	}
	else
	{
	return 0; 
	}
}
int main()
{
	int n = 50;
	if ( n < 0 )
	{
	return 0;
	}
	else
	{
	cout<< fun(n);
	}
	return 0;
}

Output:

C++ Tricks for Competitive Programming

As you can see, we have spent lot of time for completing this if else statements but if we use ternary operator in same code we will surely get benefit. Let’s see the below code to get more clear idea.

Code using ternary operator:

#include <iostream>
using namespace std;
int fun(int n)
{
     int x;
	n > 100 ? x= 1: x= 0;
	return x;
}
int main()
{
	int n = 50;
	n < 0 ? cout<< 0 : cout << fun( n );
	return 0;
}

Output:

C++ Tricks for Competitive Programming

6. Two variables swapping without use of third variable

Swapping is a very common process in programming problems. Many famous sorting algorithms need swapping as a basic process. So, you can see the importance of swapping. In this process, mainly the values of two variables are interchanged. If we have to swap two numbers then it is necessary to take one more variable to store value. But just think about a big set of data which is to be sorted. Now you have to swap. For every swapping you have to take one extra variable. This thing will surely increase the time complexity. You can reduce this extra complexity by doing xor operation on two variables.

Code using extra variable:

#include <iostream>
using namespace std;
int main()
{
	int a = 50;
	int b = 10;
	cout << a<< endl;
	cout << b<< endl;
	int c = a;
	a = b;
	b = c;
	cout << a<< endl;
	cout << b<< endl;
	return 0;
}

Output:

C++ Tricks for Competitive Programming

As you can see, we have declared one new variable to swap the variable. BY using the XOR operation we can do it more efficiently.  Let’s see the below code to get more clear idea.

Code using ternary operator:

#include <iostream>
using namespace std;
int main()
{ 
int a = 50;
	int b = 10;
	cout << a<<endl;
	cout << b<< endl;
	a ^= b;
	b ^= a;
	a ^= b;
	cout << a<< endl;
	cout << b<< endl;
	return 0; 
}

Output:

C++ Tricks for Competitive Programming

7. Multiplication by 2 and division by 2 easy method

Division by 2 and multiplication by 2 are very common operations which are used in many problems. It is very easy thing to multiply or divide. But just think about the situation when you have to multiply in a loop and the number is very big. The same thing can happen in the case of division. For this reason we can use right shift and left shift operations instead of multiplication and division.

Code using normal multiplication and division:

#include <iostream>
using namespace std;
int main()
{
	int a = 5;
	int b = 1;
	for ( int I = 0; I < a; I++ )
	{
	cout << b<< endl;
	b = b*2;
	}
	for ( int I = 0; I < a; I++ )
	{
	cout << b<< endl;
	b = b/2;
	}
	return 0;
}

Output:

C++ Tricks for Competitive Programming

As you can see, the time complexity increases automatically. But if we use shift operations we will surely get benefit.  Let’s see the below code to get more clear idea.

Code using shift operator:

#include <iostream>
using namespace std;
int main()
{ 
int a = 50;
	int b = 10;
	for ( int I = 0; I < a; I++ )
	{
	cout << b;
	//multiplication with 2
	b = b << 1;
	}
	for ( int I = 0; I < a; I++ )
	{
	cout << b;
	// division by 2
	b = b >> 1;
	}
	return 0;
}

Output:

C++ Tricks for Competitive Programming