// C++ program for the above approach

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

// Define a class named State
class State {
private:
	// Item
	struct item {
		char value;
		State* next;
	};

	// Three states
	item Input1;
	item Input2;
	char m_out;

public:
	// Constructor
	State()
		: Input1{ ' ', nullptr },
		Input2{ ' ', nullptr },
		m_out{ ' ' }
	{
	}

	// Member functions
	static State* m_ptr;
	void Initialize(item input1,
					item input2,
					char out);
	static char Transition(char x);
	static string Traverse(string& str,
						int n);
};

// Global object pointer points to
// current state
State* State::m_ptr{ nullptr };

// Function that initializes the states
// with appropriate values
void State::Initialize(item input1,
					item input2,
					char out)
{
	Input1 = input1;
	Input2 = input2;
	m_out = out;
}

// Transition function that takes each
// character of string
char State::Transition(char x)
{
	char ch{};

	// Prints the output
	if ((*m_ptr).Input1.value == x) {

		// Output the current state
		cout << (*m_ptr).m_out;
		ch = (*m_ptr).m_out;

		// Next input state
		m_ptr = (*m_ptr).Input1.next;
	}
	else {

		// Output the current state
		cout << (*m_ptr).m_out;
		ch = (*m_ptr).m_out;

		// Next input state
		m_ptr = (*m_ptr).Input2.next;
	}

	// Return ch
	return ch;
}

// Takes the whole string and pass
// it through machine
string State::Traverse(string& str,
					int n)
{
	string str1{};

	// Add all the transition state to
	// the string str1
	for (int i = 0; i < n; i++)
		str1 += Transition(str[i]);

	// Append output
	str1 += (*m_ptr).m_out;
	cout << (*m_ptr).m_out << endl;

	// Return str1
	return str1;
}

// Function that create states and
// produce output
string mooreOut(string str, int n)
{
	State q1, q2, q3, q4;

	// Initializing the states
	q1.Initialize({ 'a', &q2 },
				{ 'b', &q1 }, '0');
	q2.Initialize({ 'a', &q2 },
				{ 'b', &q3 }, '0');
	q3.Initialize({ 'a', &q2 },
				{ 'b', &q4 }, '0');
	q4.Initialize({ 'a', &q2 },
				{ 'b', &q1 }, '1');
	State::m_ptr = &q1;

	// Traverse the string str1
	string str1{ State::Traverse(str, n) };
	return str1;
}

// Function that counts the occurrences
// of 1 in the output string
int countStr(string& str, int n)
{
	int count{};

	// Count the 1s in str
	for (int i = 0; i < n; i++) {
		if (str[i] == '1')
			count++;
	}

	// Return count
	return count;
}

// Driver Code
int main()
{

	// Given string
	string str{ "babbabbabbb" };

	int n{ static_cast<int>(str.length()) };

	// Function Call
	string str1{ mooreOut(str, n) };
	int n1{ static_cast<int>(str.length()) };

	// Print the count of substring
	cout << "abb occurs " << countStr(str1, n1)
		<< " times\n";
	return 0;
}
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Read inputs from stdin

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#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}