// lower bound small index which is grater then  equal to k arr[ind]>=k.
// STL
// ans = lower_bound(a.begin() , a.end() , x) - a.begin();

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

int  lower_boundd(vector<int>&a , int n , int k , int &ans)
{
  int low = 0 , high = n-1;
  while(low <= high)
  {
    int mid = (low + high) / 2;
    if(a[mid] > k)
    {
      ans = mid ;
      high = mid - 1;
    }
    else
    {
      low = mid + 1; 
    }
  }
  return ans;
}
// lower bound small index which is grater then  equal to k arr[ind]>k.
// int  upper_boundd(vector<int>&a , int n , int k , int &ans)
// {
//   int low = 0 , high = n-1;
//   while(low <= high)
//   {
//     int mid = (low + high) / 2;
//     if(a[mid] > k)
//     {
//       ans = mid ;
//       high = mid - 1;
//     }
//     else
//     {
//       low = mid + 1; 
//     }
//   }
//   return ans;
// }
int main() 
{
    vector<int>a{5,7,7,8,8,10};
    int n = 6;
    int k = 8;
    int ans = 6;
    lower_boundd(a , n , k , ans);
    // upper_boundd(a , n, k , ans);
    cout<<ans;
}
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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
}