/*// CPP program to find infix for 
// a given postfix. 
#include <bits/stdc++.h> 
using namespace std; 

bool isOperand(char x) 
{ 
return (x >= 'a' && x <= 'z') || 
		(x >= 'A' && x <= 'Z'); 
} 

// Get Infix for a given postfix 
// expression 
string getInfix(string exp) 
{ 
	stack<string> s; 

	for (int i=0; exp[i]!='\0'; i++) 
	{ 
		// Push operands 
		if (isOperand(exp[i])) 
		{ 
		string op(1, exp[i]); 
		s.push(op); 
		} 

		// We assume that input is 
		// a valid postfix and expect 
		// an operator. 
		else
		{ 
			string op1 = s.top(); 
			s.pop(); 
			string op2 = s.top(); 
			s.pop(); 
			s.push("(" + op2 + exp[i] + 
				op1 + ")"); 
		} 
	} 

	// There must be a single element 
	// in stack now which is the required 
	// infix. 
	return s.top(); 
} 

// Driver code 
int main() 
{ 
	string exp = "ab*c+"; 
	cout << getInfix(exp); 
	return 0; 
} 
*/



// C++ Program to convert prefix to Infix
#include <iostream>
#include <stack>
using namespace std;

// function to check if character is operator or not
bool isOperator(char x) {
switch (x) {
case '+':
case '-':
case '/':
case '*':
	return true;
}
return false;
}

// Convert prefix to Infix expression
string preToInfix(string pre_exp) {
stack<string> s;

// length of expression
int length = pre_exp.size();

// reading from right to left
for (int i = length - 1; i >= 0; i--) {

	// check if symbol is operator
	if (isOperator(pre_exp[i])) {

	// pop two operands from stack
	string op1 = s.top(); s.pop();
	string op2 = s.top(); s.pop();

	// concat the operands and operator
	string temp = "(" + op1 + pre_exp[i] + op2 + ")";

	// Push string temp back to stack
	s.push(temp);
	}

	// if symbol is an operand
	else {

	// push the operand to the stack
	s.push(string(1, pre_exp[i]));
	}
}

// Stack now contains the Infix expression
return s.top();
}

// Driver Code
int main() {
string pre_exp = "*-A/BC-/AKL";
cout << "Infix : " << preToInfix(pre_exp);
return 0;
}
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Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#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
}