C++ Tutorial Index

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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

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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 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C++ Convert Int to String

In fact, the conversion of numbers to strings or vice versa represents a significant paradigm change. We often need to convert a number to a string or a string to a number in general, or more especially in competitive programming. But we can't do so fluently because we have inadequate knowledge of some crucial skills. In this article, a few approaches to doing this work are discussed.

Number to String Conversion in C++:

The three main ways to change a number into a string are as follows:

  • By using string Stream 
  • By using to_string()
  • By using boost lexical cast

First approach: String Streams:

In this method, a stream object is declared that first inserts a number as a stream into an object before using "str()" to carry out the internal conversion of a number to a string.

C++ Program:

#include<iostream> //header files
#include <sstream> 
#include <string>


using namespace std;
int main()
{
	//initializing an integer
	int value = 2001;


	ostringstream strng1;


	strng1 << value;


	// changing number into string
	string s1 = strng1.str();


	//printing the string
	cout << " The freshly created number string is: ";
	cout << s1 << endl;


	return 0;
}

Output:

The freshly created number string is: 2001
Time Complexity:  O(n)
Space Complexity:  O(n)

Second approach: to_string():

The to_string() method takes a number, which can be of any data type, and returns it as the specified string.

C++ Program:

#include <iostream> //header files
#include <string>


using namespace std;




int main()
{
	//initializing an integer number
	int inval = 25;
	
	//initializing a floating number
	float flval = 15.03;


	//changing int to string
	string strng_i= to_string (inval);


	// changing float to string
	string strng_f = to_string (flval);


	// printing the converted strings
	cout << "In string, the integer is: ";
	cout << strng_i << endl;
	cout << "In string, the float is: ";
	cout << strng_f << endl;


	return 0;
}

Output:

In string, the integer is: 25
In string, the float is: 15.030000
Time Complexity: O(n)
Auxiliary Space: O(n)

Third approach:  Boost Lexical Cast:

Similar to how string conversion works, the "lexical cast()" method stays the same, but the argument list changes when using "boost lexical cast," becoming "lexical_cast(num_var)".

C++ Program:

#include <boost/lexical_cast.hpp> //header files
#include <iostream>
#include <string> 
using namespace std;




int main()
{
	//initializing a floating number
	float fl_val = 17.6;


	//initializing an integer number
	int in_val = 21;


	// changing float to string
	string strng_f = boost::lexical_cast<string>(fl_val);


	//changing int to string
	string strng_i = boost::lexical_cast<string>(in_val);


	// printing the converted strings
	cout << "In string, the float is: ";
	cout << strng_f << endl;
	cout << "In string, the integer is: ";
	cout << strng_i << endl;


	return 0;
}

Output:

In string, the float is: 17.6
In string, the integer is: 21
Time Complexity: O(n)
Auxiliary Space: O(n)