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

class node{
  public:
    int data;
    node* left;
    node* right;
    
    node(int val){
      data=val;
      left=NULL;
      right=NULL;
    }
};


bool isLeaf(node* root){
  if(root->left || root->right){
    return false;
  }
  return true;
}

void addLeftBoundary(node* root,vector<int> &v){
  node* n = root->left;
  while(n){
    if(!isLeaf(n)){
      v.push_back(n->data);
    }
    if(n->left){
      n=n->left;
    } else {
      n=n->right;
    }
  }
}

void addleafs(node* root,vector<int> &v){
  if(isLeaf(root)){
    v.push_back(root->data);
    return;
  }

  if(root->left) addleafs(root->left,v);
  if(root->right) addleafs(root->right,v);
}

void addRightBoundary(node* root,vector<int> &v){
  node* n = root->right;
  vector<int> vec;
  while(n){
    if(!isLeaf(n)){
      vec.push_back(n->data);
    }
    if(n->right){
      n=n->right;
    } else {
      n=n->left;
    }
  }
  for(int i=vec.size()-1;i>=0;i--){
    v.push_back(vec[i]);
  }
  
}

int main(){
  node* root = new node(1);
  root->left=new node(2);
  root->right=new node(3);
  root->left->left=new node(4);
  root->left->right=new node(5);
  root->right->left=new node(6);
  root->right->right=new node(7);
  
  vector<int> v;
  if(root==NULL){
    cout<<"No elements!!";
  }
  if(!isLeaf(root)){
    v.push_back(root->data);
  }
  addLeftBoundary(root,v);
  addleafs(root,v);
  addRightBoundary(root,v);
  
  for(auto i: v){
    cout<<i<<" ";
  }
}

/*  
      1 
    /   \
   2     3 
  / \   / \
 4   5    7

*/
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
}