#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 operators 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;
}
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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;
}
C++ is a widely used middle-level programming language.
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.
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;
}
For loop is used to iterate a set of statements based on a condition.
for(Initialization; Condition; Increment/decrement){
//code
}
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
}
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);
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.
return_type function_name(parameters);
function_name (parameters)
return_type function_name(parameters) {
// code
}