C++ Programming Code Examples
C++ > Sorting Searching Code Examples
C++ Program to Implement Counting Sort
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/* C++ Program to Implement Counting Sort
This is a C++ program to sort the given data using Counter Sort.
- Counter sort implements on a given finite range (k) of the integers.
- It counts the occurrence of each element.
- Since it maintains the counter of each integer in the range space complexity is O(k).
- The time complexity is O(n+k).
- count the number of occurrences of each element.
- Store it in the array of size same as the range of data input.
- Use the element value to refer the counter index.
- Display the result.
- Exit. */
#include<iostream>
using namespace std;
// A function implementing Counter sort.
void CounterSort(int a[], int n, int r, int lower)
{
int i, j = 0, counter[r] = {0};
// Counting the number occurrence of each element.
for(i=0; i<n; i++)
counter[a[i]-lower]++;
i=0;
// placing the elements back into array.
while(i < r)
{
flag:
a[j] = lower+i;
j++;
counter[i]--;
// place the same element until its counter is zero.
if(counter[i] > 0)
goto flag;
i++;
}
}
int main()
{
int n, i, range, ulimit, llimit;
cout<<"\nEnter the number of data element to be sorted: ";
cin>>n;
cout<<"\nEnter the lower and upper limit of the data to be entered: ";
cin>>llimit>>ulimit;
// Range of the input data.
range = ulimit-llimit+1;
int arr[n];
for(i = 0; i < n; i++)
{
cout<<"Enter element "<<i+1<<": ";
cin>>arr[i];
}
CounterSort(arr, n, range, llimit);
// Printing the sorted data.
cout<<"\nSorted Data ";
for (i = 0; i < n; i++)
cout<<"->"<<arr[i];
return 0;
}
Nested Loop Statement in C++
C supports nesting of loops in C. Nesting of loops is the feature in C that allows the looping of statements inside another loop. Any number of loops can be defined inside another loop, i.e., there is no restriction for defining any number of loops. The nesting level can be defined at n times. You can define any type of loop inside another loop; for example, you can define 'while' loop inside a 'for' loop.
A loop inside another loop is called a nested loop. The depth of nested loop depends on the complexity of a problem. We can have any number of nested loops as required. Consider a nested loop where the outer loop runs n times and consists of another loop inside it. The inner loop runs m times. Then, the total number of times the inner loop runs during the program execution is n*m.
Syntax for Nested Loop Statement in C++
Outer_loop
{
Inner_loop
{
// inner loop statements.
}
// outer loop statements.
}
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/* nested loop statement in C++ language */
// C++ program that uses nested for loop to print a 2D matrix
#include <bits/stdc++.h>
using namespace std;
#define ROW 3
#define COL 3
// Driver program
int main()
{
int i, j;
// Declare the matrix
int matrix[ROW][COL] = { { 4, 8, 12 },
{ 16, 20, 24 },
{ 28, 32, 36 } };
cout << "Given matrix is \n";
// Print the matrix using nested loops
for (i = 0; i < ROW; i++) {
for (j = 0; j < COL; j++)
cout << matrix[i][j];
cout << "\n";
}
return 0;
}
What is an Array in C++ Language
An array is defined as the collection of similar type of data items stored at contiguous memory locations. Arrays are the derived data type in C++ programming language which can store the primitive type of data such as int, char, double, float, etc. It also has the capability to store the collection of derived data types, such as pointers, structure, etc. The array is the simplest data structure where each data element can be randomly accessed by using its index number.
C++ array is beneficial if you have to store similar elements. For example, if we want to store the marks of a student in 6 subjects, then we don't need to define different variables for the marks in the different subject. Instead of that, we can define an array which can store the marks in each subject at the contiguous memory locations.
By using the array, we can access the elements easily. Only a few lines of code are required to access the elements of the array.
Properties of Array
The array contains the following properties.
• Each element of an array is of same data type and carries the same size, i.e., int = 4 bytes.
• Elements of the array are stored at contiguous memory locations where the first element is stored at the smallest memory location.
• Elements of the array can be randomly accessed since we can calculate the address of each element of the array with the given base address and the size of the data element.
Advantage of C++ Array
• 1) Code Optimization: Less code to the access the data.
• 2) Ease of traversing: By using the for loop, we can retrieve the elements of an array easily.
• 3) Ease of sorting: To sort the elements of the array, we need a few lines of code only.
• 4) Random Access: We can access any element randomly using the array.
Disadvantage of C++ Array
• 1) Allows a fixed number of elements to be entered which is decided at the time of declaration. Unlike a linked list, an array in C++ is not dynamic.
• 2) Insertion and deletion of elements can be costly since the elements are needed to be managed in accordance with the new memory allocation.
Declaration of C++ Array
To declare an array in C++, a programmer specifies the type of the elements and the number of elements required by an array as follows
type arrayName [ arraySize ];
double balance[10];
Initializing Arrays
You can initialize an array in C++ either one by one or using a single statement as follows
double balance[5] = {850, 3.0, 7.4, 7.0, 88};
double balance[] = {850, 3.0, 7.4, 7.0, 88};
Accessing Array Elements
An element is accessed by indexing the array name. This is done by placing the index of the element within square brackets after the name of the array.
double salary = balance[9];
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/* arrays in C++ Language */
#include <iostream>
using namespace std;
int main() {
// initialize an array without specifying size
double numbers[] = {7, 5, 6, 12, 35, 27};
double sum = 0;
double count = 0;
double average;
cout << "The numbers are: ";
// print array elements
// use of range-based for loop
for (const double &n : numbers) {
cout << n << " ";
// calculate the sum
sum += n;
// count the no. of array elements
++count;
}
// print the sum
cout << "\nTheir Sum = " << sum << endl;
// find the average
average = sum / count;
cout << "Their Average = " << average << endl;
return 0;
}
main() Function in C++
A program shall contain a global function named main, which is the designated start of the program in hosted environment. main() function is the entry point of any C++ program. It is the point at which execution of program is started. When a C++ program is executed, the execution control goes directly to the main() function. Every C++ program have a main() function.
Syntax for main() Function in C++
void main()
{
............
............
}
void
void is a keyword in C++ language, void means nothing, whenever we use void as a function return type then that function nothing return. here main() function no return any value.
main
main is a name of function which is predefined function in C++ library.
In place of void we can also use int return type of main() function, at that time main() return integer type value.
1) It cannot be used anywhere in the program
a) in particular, it cannot be called recursively
b) its address cannot be taken
2) It cannot be predefined and cannot be overloaded: effectively, the name main in the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace).
3) It cannot be defined as deleted or (since C++11) declared with C language linkage, constexpr (since C++11), consteval (since C++20), inline, or static.
4) The body of the main function does not need to contain the return statement: if control reaches the end of main without encountering a return statement, the effect is that of executing return 0;.
5) Execution of the return (or the implicit return upon reaching the end of main) is equivalent to first leaving the function normally (which destroys the objects with automatic storage duration) and then calling std::exit with the same argument as the argument of the return. (std::exit then destroys static objects and terminates the program).
6) (since C++14) The return type of the main function cannot be deduced (auto main() {... is not allowed).
7) (since C++20) The main function cannot be a coroutine.
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/* simple code example by main() function in C++ */
#include <iostream>
using namespace std;
int main() {
int day = 4;
switch (day) {
case 1:
cout << "Monday";
break;
case 2:
cout << "Tuesday";
break;
case 3:
cout << "Wednesday";
break;
case 4:
cout << "Thursday";
break;
case 5:
cout << "Friday";
break;
case 6:
cout << "Saturday";
break;
case 7:
cout << "Sunday";
break;
}
return 0;
}
For Loop Statement in C++
In computer programming, loops are used to repeat a block of code. For example, when you are displaying number from 1 to 100 you may want set the value of a variable to 1 and display it 100 times, increasing its value by 1 on each loop iteration. When you know exactly how many times you want to loop through a block of code, use the for loop instead of a while loop. A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times.
Syntax of For Loop Statement in C++
for (initialization; condition; update) {
// body of-loop
}
initialization
initializes variables and is executed only once.
condition
if true, the body of for loop is executed, if false, the for loop is terminated.
update
updates the value of initialized variables and again checks the condition.
A new range-based for loop was introduced to work with collections such as arrays and vectors.
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/* For Loop Statement in C++ Language */
// C++ program to find the sum of first n natural numbers
// positive integers such as 1,2,3,...n are known as natural numbers
#include <iostream>
using namespace std;
int main() {
int num, sum;
sum = 0;
cout << "Enter a positive integer: ";
cin >> num;
for (int i = 1; i <= num; ++i) {
sum += i;
}
cout << "Sum = " << sum << endl;
return 0;
}
Standard Output Stream (cout) in C++
The cout is a predefined object of ostream class. It is connected with the standard output device, which is usually a display screen. The cout is used in conjunction with stream insertion operator (<<) to display the output on a console. On most program environments, the standard output by default is the screen, and the C++ stream object defined to access it is cout.
Syntax for cout in C++
cout << var_name;
//or
cout << "Some String";
<<
is the insertion operator
var_name
is usually a variable, but can also be an array element or elements of containers like vectors, lists, maps, etc.
The "c" in cout refers to "character" and "out" means "output". Hence cout means "character output".
The cout object is used along with the insertion operator << in order to display a stream of characters.
The << operator can be used more than once with a combination of variables, strings, and manipulators.
cout is used for displaying data on the screen. The operator << called as insertion operator or put to operator. The Insertion operator can be overloaded. Insertion operator is similar to the printf() operation in C. cout is the object of ostream class. Data flow direction is from variable to output device. Multiple outputs can be displayed using cout.
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/* standard output stream (cout) in C++ language */
#include <iostream>
using namespace std;
int main() {
string str = "Do not interrupt me";
char ch = 'm';
// use cout with write()
cout.write(str,6);
cout << endl;
// use cout with put()
cout.put(ch);
return 0;
}
#include Directive in C++
#include is a way of including a standard or user-defined file in the program and is mostly written at the beginning of any C/C++ program. This directive is read by the preprocessor and orders it to insert the content of a user-defined or system header file into the following program. These files are mainly imported from an outside source into the current program. The process of importing such files that might be system-defined or user-defined is known as File Inclusion. This type of preprocessor directive tells the compiler to include a file in the source code program.
Syntax for #include Directive in C++
#include "user-defined_file"
#include <header_file>
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/* using #include directive in C language */
#include <stdio.h>
int main()
{
/*
* C standard library printf function
* defined in the stdio.h header file
*/
printf("I love you Clementine");
printf("I love you so much");
printf("HappyCodings");
return 0;
}
Namespaces in C++ Language
Consider a situation, when we have two persons with the same name, jhon, in the same class. Whenever we need to differentiate them definitely we would have to use some additional information along with their name, like either the area, if they live in different area or their mother's or father's name, etc.
Same situation can arise in your C++ applications. For example, you might be writing some code that has a function called xyz() and there is another library available which is also having same function xyz(). Now the compiler has no way of knowing which version of xyz() function you are referring to within your code.
A namespace is designed to overcome this difficulty and is used as additional information to differentiate similar functions, classes, variables etc. with the same name available in different libraries. Using namespace, you can define the context in which names are defined. In essence, a namespace defines a scope.
Defining a Namespace
A namespace definition begins with the keyword namespace followed by the namespace name as follows:
namespace namespace_name {
// code declarations
}
name::code; // code could be variable or function.
Using Directive
You can also avoid prepending of namespaces with the using namespace directive. This directive tells the compiler that the subsequent code is making use of names in the specified namespace.
Discontiguous Namespaces
A namespace can be defined in several parts and so a namespace is made up of the sum of its separately defined parts. The separate parts of a namespace can be spread over multiple files.
So, if one part of the namespace requires a name defined in another file, that name must still be declared. Writing a following namespace definition either defines a new namespace or adds new elements to an existing one:
namespace namespace_name {
// code declarations
}
Nested Namespaces
Namespaces can be nested where you can define one namespace inside another name space as follows:
namespace namespace_name1 {
// code declarations
namespace namespace_name2 {
// code declarations
}
}
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/* namespaces in C++ language */
// A C++ code to demonstrate that we can define
// methods outside namespace.
#include <iostream>
using namespace std;
// Creating a namespace
namespace ns
{
void display();
class happy
{
public:
void display();
};
}
// Defining methods of namespace
void ns::happy::display()
{
cout << "ns::happy::display()\n";
}
void ns::display()
{
cout << "ns::display()\n";
}
// Driver code
int main()
{
ns::happy obj;
ns::display();
obj.display();
return 0;
}
Relational Operators in C++
A relational operator is used to check the relationship between two operands. C++ Relational Operators are used to relate or compare given operands. Relational operations are like checking if two operands are equal or not equal, greater or lesser, etc.
Relational Operators are also called Comparison Operators.
• == Is Equal To 4 == 9 gives us false
• != Not Equal To 4 != 9 gives us true
• > Greater Than 4 > 9 gives us false
• < Less Than 4 < 9 gives us true
• >= Greater Than or Equal To 4 >= 9 give us false
• <= Less Than or Equal To 4 <= 9 gives us true
==
Equal To Operator (==) is used to compare both operands and returns 1 if both are equal or the same, and 0 represents the operands that are not equal.
The equal to == operator returns
true - if both the operands are equal or the same
false - if the operands are unequal
int x = 10;
int y = 15;
int z = 10;
x == y // false
x == z // true
The relational operator == is not the same as the assignment operator =. The assignment operator = assigns a value to a variable, constant, array, or vector. It does not compare two operands.
!=
Not Equal To Operator (!=) is the opposite of the Equal To Operator and is represented as the (!=) operator. The Not Equal To Operator compares two operands and returns 1 if both operands are not the same; otherwise, it returns 0.
The not equal to != operator returns
true - if both operands are unequal
false - if both operands are equal.
int x = 10;
int y = 15;
int z = 10;
x != y // true
x != z // false
>
Greater than Operator (>) checks the value of the left operand is greater than the right operand, and if the statement is true, the operator is said to be the Greater Than Operator.
The greater than > operator returns
true - if the left operand is greater than the right
false - if the left operand is less than the right
int x = 10;
int y = 15;
x > y // false
y > x // true
<
Less than Operator (<) is used to check whether the value of the left operand is less than the right operand, and if the statement is true, the operator is known as the Less than Operator.
The less than operator < returns
true - if the left operand is less than the right
false - if the left operand is greater than right
int x = 10;
int y = 15;
x < y // true
y < x // false
>=
Greater than Equal To Operator (>=) checks whether the left operand's value is greater than or equal to the right operand. If the statement is true, the operator is said to be the Greater than Equal to Operator.
The greater than or equal to >= operator returns
true - if the left operand is either greater than or equal to the right
false - if the left operand is less than the right
int x = 10;
int y = 15;
int z = 10;
x >= y // false
y >= x // true
z >= x // true
<=
Less than Equal To Operator (<=) checks whether the value of the left operand is less than or equal to the right operand, and if the statement is true, the operator is said to be the Less than Equal To Operator.
The less than or equal to operator <= returns
true - if the left operand is either less than or equal to the right
false - if the left operand is greater than right
int x = 10;
int y = 15;
x > y // false
y > x // true
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/* Relational Operators are used for the comparison of the values of two operands. For example, checking if one operand is equal to the other operand or not, an operand is greater than the other operand or not, etc. Some of the relational operators are (==, >= , <= ). */
#include <iostream>
using namespace std;
main() {
int a = 21;
int b = 10;
int c ;
if( a == b ) {
cout << "Line 1 - a is equal to b" << endl ;
} else {
cout << "Line 1 - a is not equal to b" << endl ;
}
if( a < b ) {
cout << "Line 2 - a is less than b" << endl ;
} else {
cout << "Line 2 - a is not less than b" << endl ;
}
if( a > b ) {
cout << "Line 3 - a is greater than b" << endl ;
} else {
cout << "Line 3 - a is not greater than b" << endl ;
}
/* Let's change the values of a and b */
a = 5;
b = 20;
if( a <= b ) {
cout << "Line 4 - a is either less than \ or equal to b" << endl ;
}
if( b >= a ) {
cout << "Line 5 - b is either greater than \ or equal to b" << endl ;
}
return 0;
}
Standard Input Stream (cin) in C++
The cin object is used to accept input from the standard input device i.e. keyboard. It is defined in the iostream header file. C++ cin statement is the instance of the class istream and is used to read input from the standard input device which is usually a keyboard. The extraction operator(>>) is used along with the object cin for reading inputs. The extraction operator extracts the data from the object cin which is entered using the keyboard.
Syntax for Standard Input Stream (cin) in C++
cin >> var_name;
>>
is the extraction operator.
var_name
is usually a variable, but can also be an element of containers like arrays, vectors, lists, etc.
The "c" in cin refers to "character" and "in" means "input". Hence cin means "character input".
The cin object is used along with the extraction operator >> in order to receive a stream of characters.
The >> operator can also be used more than once in the same statement to accept multiple inputs.
The cin object can also be used with other member functions such as getline(), read(), etc. Some of the commonly used member functions are:
• cin.get(char &ch): Reads an input character and stores it in ch.
• cin.getline(char *buffer, int length): Reads a stream of characters into the string buffer, It stops when:
it has read length-1 characters or
when it finds an end-of-line character '\n' or the end of the file eof.
• cin.read(char *buffer, int n): Reads n bytes (or until the end of the file) from the stream into the buffer.
• cin.ignore(int n): Ignores the next n characters from the input stream.
• cin.eof(): Returns a non-zero value if the end of file (eof) is reached.
The prototype of cin as defined in the iostream header file is: extern istream cin; The cin object in C++ is an object of class istream. It is associated with the standard C input stream stdin.
The cin object is ensured to be initialized during or before the first time an object of type ios_base::Init is constructed.
After the cin object is constructed, cin.tie() returns &cout. This means that any formatted input operation on cin forces a call to cout.flush() if any characters are pending for output.
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/* Standard Input Stream (cin) in C++ language */
// cin with Member Functions
#include <iostream>
using namespace std;
int main() {
char name[20], address[20];
cout << "Name: ";
// use cin with getline()
cin.getline(name, 20);
cout << "Address: ";
cin.getline(address, 20);
cout << endl << "You entered " << endl;
cout << "Name = " << name << endl;
cout << "Address = " << address;
return 0;
}
While Loop Statement in C++
In while loop, condition is evaluated first and if it returns true then the statements inside while loop execute, this happens repeatedly until the condition returns false. When condition returns false, the control comes out of loop and jumps to the next statement in the program after while loop.
The important point to note when using while loop is that we need to use increment or decrement statement inside while loop so that the loop variable gets changed on each iteration, and at some point condition returns false. This way we can end the execution of while loop otherwise the loop would execute indefinitely. A while loop that never stops is said to be the infinite while loop, when we give the condition in such a way so that it never returns false, then the loops becomes infinite and repeats itself indefinitely.
Syntax for While Loop Statement in C++
while (condition) {
// body of the loop
}
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/* While Loop Statement in C++ language */
// program to find the sum of positive numbers
// if the user enters a negative number, the loop ends
// the negative number entered is not added to the sum
#include <iostream>
using namespace std;
int main() {
int number;
int sum = 0;
// take input from the user
cout << "Enter a number: ";
cin >> number;
while (number >= 0) {
// add all positive numbers
sum += number;
// take input again if the number is positive
cout << "Enter a number: ";
cin >> number;
}
// display the sum
cout << "\nThe sum is " << sum << endl;
return 0;
}
Goto Statement in C++
In C++, goto is a jump statement and sometimes also referred as unconditional jump statement. It can be used to jump from goto to a labeled statement within the same function. The target label must be within the same file and context.
Please note that the use of goto statement is highly discouraged in any programming language because it makes difficult to trace the control flow of a program, making hard to understand and modify the program.
Syntax for Goto Statement in C++
goto label;
...
...
...
label: statement;
label
the destination statement
• The use of goto statement is highly discouraged as it makes the program logic very complex.
• use of goto makes the task of analyzing and verifying the correctness of programs (particularly those involving loops) very difficult.
• Use of goto can be simply avoided using break and continue statements.
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/* In C++ programming, the goto statement is used for altering the normal sequence of program execution by transferring control to some other part of the program. */
// This program calculates the average of numbers entered by the user.
// If the user enters a negative number, it ignores the number and
// calculates the average number entered before it.
# include <iostream>
using namespace std;
int main()
{
float num, average, sum = 0.0;
int i, n;
cout << "Maximum number of inputs: ";
cin >> n;
for(i = 1; i <= n; ++i)
{
cout << "Enter n" << i << ": ";
cin >> num;
if(num < 0.0)
{
// Control of the program move to jump:
goto jump;
}
sum += num;
}
jump:
average = sum / (i - 1);
cout << "\nAverage = " << average;
return 0;
}
If Else Statement in C++
In computer programming, we use the if statement to run a block code only when a certain condition is met. An if statement can be followed by an optional else statement, which executes when the boolean expression is false. There are three forms of if...else statements in C++:
• if statement,
• if...else statement,
• if...else if...else statement,
Syntax for If Statement in C++
if (condition) {
// body of if statement
}
Syntax for If...Else Statement
if (condition) {
// block of code if condition is true
}
else {
// block of code if condition is false
}
Syntax for If...Else...Else If Statement in C++
if (condition1) {
// code block 1
}
else if (condition2){
// code block 2
}
else {
// code block 3
}
Syntax for If Else If Ladder in C++
if (condition)
statement 1;
else if (condition)
statement 2;
.
.
else
statement;
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/* If Else Statement in C++ Language */
#include <iostream>
using namespace std;
int main () {
// local variable declaration:
int a = 100;
// check the boolean condition
if( a < 20 ) {
// if condition is true then print the following
cout << "a is less than 20;" << endl;
} else {
// if condition is false then print the following
cout << "a is not less than 20;" << endl;
}
cout << "value of a is : " << a << endl;
return 0;
}
First we have to clear about what is transpose of a matrix. Its to replace the number of rows with number of colums, vice versa to make a new matrix. So for example if a matrix 'A' has
This C++ Program implement "Affine Cipher". The affine cipher is a type of Monoalphabetic Substitution Cipher, wherein each letter in an alphabet is mapped to its numeric equivalent,
A "Structure Distance" containing two data members (inch and feet) is declared to store the distance in inch-feet system. Here, two structure variables d1 and d2 are created to