 #include<iostream>
#include<stack>
using namespace std;
// defines the Boolean function for operator, operand, equalOrhigher precedence and the string conversion function.
bool IsOperator(char);
bool IsOperand(char);
bool eqlOrhigher(char, char); string convert(string);
int main()
{
string infix_expression, postfix_expression; int ch;
do
{
cout << " Enter an infix expression: ";
cin >> infix_expression;
postfix_expression = convert(infix_expression);
cout << "\n Your Infix expression is: " << infix_expression; cout << "\n Postfix expression is: " << postfix_expression; cout << "\n \t Do you want to enter infix expression (1/ 0)?"; cin >> ch;
//cin.ignore();
} while(ch == 1); return 0;
}
// define the IsOperator() function to validate whether any symbol is operator. /* If the symbol is operator, it returns true, otherwise false. */
bool IsOperator(char c)
{
if(c == '+' || c == '-' || c == '*' || c == '/' || c == '^' ) return true;
return false;
}
// IsOperand() function is used to validate whether the character is operand.
bool IsOperand(char c)
{
if( c >= 'A' && c <= 'Z') /* Define the character in between A to Z. If not, it returns False.*/ return true;
if (c >= 'a' && c <= 'z') // Define the character in between a to z. If not, it returns False. */ return true;
if(c >= '0' && c <= '9') // Define the character in between 0 to 9. If not, it returns False. */ return true;
return false;
}
// here, precedence() function is used to define the precedence to the operator. int precedence(char op)
{
if(op == '+' || op == '-') /* it defines the lowest precedence */
return 1;
if (op == '*' || op == '/')

 return 2;
if(op == '^') /* exponent operator has the highest precedence *
return 3;
return 0;
}
/* The eqlOrhigher() function is used to check the higher or equal precedence of the two operato rs in infix expression. */
bool eqlOrhigher (char op1, char op2)
{
int p1 = precedence(op1);
int p2 = precedence(op2);
if (p1 == p2)
{
if (op1 == '^' )
return false;
return true;
}
return (p1>p2 ? true : false);
}
/* string convert() function is used to convert the infix expression to the postfix expression of the Stack */
string convert(string infix) {
stack <char> S;
string postfix ="";
char ch;
S.push( '(' ); infix += ')';
for(int i = 0; i<infix.length(); i++) {
ch = infix[i];
if(ch == ' ')
continue;
else if(ch == '(')
S.push(ch);
else if(IsOperand(ch))
postfix += ch;
else if(IsOperator(ch))
{
while(!S.empty() && eqlOrhigher(S.top(), ch)) {
postfix += S.top();
S.pop();
}
S.push(ch);
}
else if(ch == ')')
{
while(!S.empty() && S.top() != '(')
{

 postfix += S.top(); S.pop();
}
S.pop();
}
}
return postfix;

created 3 years ago

C++ Online Compiler

Write, Run & Share C++ code online using OneCompiler's C++ online compiler for free. It's one of the robust, feature-rich online compilers for C++ language, running on the latest version 17. Getting started with the OneCompiler's C++ compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C++ and start coding!

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
}