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

vector<string> kw ={"auto","break","case","char","const","continue","default",
                            "do","double","else","enum","extern","float","for","goto",
                            "if","int","long","register","return","short","signed",
                            "sizeof","static","struct","switch","typedef","union",
                            "unsigned","void","volatile","while"};

vector<string> op ={"+","-","*","/","="};

vector<string> num ={"1","2","3","4","5","6","7","8","9","0"};

vector<string> p = {"()","(",")"};

vector<string> b = {"{","}"};

void printout(string x){
  
  if(find(kw.begin(), kw.end(), x) != kw.end()) // check x contains in keyword vector
    cout<<x<<" \tkeyword\n";
  else if(find(op.begin(), op.end(), x) != op.end())
    cout<<x<<" \toperator\n";
  else if(find(num.begin(), num.end(), x) != num.end())
    cout<<x<<" \tnumber\n";
  else if(find(p.begin(), p.end(), x) != p.end())
    cout<<x<<" \tparanthesis\n";
  else if(find(b.begin(), b.end(), x) != b.end())
    cout<<x<<" \tcurley brases\n";
  else if(x==";")
    cout<<x<<" \tseperator\n";
  else if(x.find("_")==0 || ( x[0]>='a' and x[0]<='z' )||( x[0]>='A' and x[0]<='Z' ))
    cout<<x<<" \tvalid identifier\n";
}

int main(){

  string line;
  vector<string> v;
  
  while(getline(cin, line, ' ')){ // seperate words using space( ' ' )
      v.push_back(line);
  }
  for(auto x : v)
  printout(x); // send word by word
  
  return 0;
}

/*
make sure every word is seperated with space before and after
INPUT 

void main () { 
 int _i = 4 + 5  ; 
 } 
 
*/
by

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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
}