#include <iostream>
using namespace std;

// This function performs binary search on a sorted array of integers
// and returns the index of the target element if found, or -1 otherwise.
// Precondition: arr is not null, n is the size of arr, and arr is sorted in ascending order.
// Postcondition: the function does not modify arr or n, and returns a valid index or -1.
int binary_search(int arr[], int n, int target) {
  // Invariant: the target element, if it exists, is in the range [low, high].
  // Variant: high - low + 1, which decreases by at least one in each iteration.
  int low = 0; // The lower bound of the search range
  int high = n - 1; // The upper bound of the search range
    while (low <= high) {
    // Explicit internal state: low, high, mid
    int mid = (low + high) / 2; // The middle index of the search range
    if (arr[mid] == target) {
      return mid; // Found the target element at index mid
    } else if (arr[mid] < target) {
      low = mid + 1; // Narrow the search range to the right half
    } else {
    high = mid - 1; // Narrow the search range to the left half
    }
  }
  return -1; // The target element does not exist in the array
}

int main() 
{
    int array_of_elements[]={1,2,3,4,5,6,7,8,9,10};
    int number_of_elements_in_array = sizeof(array_of_elements) / sizeof(array_of_elements[0]);;
    int target_element=5;
    cout << "array_of_elements = ";
    // Loop over the array and print each element
    for (int i = 0; i < number_of_elements_in_array; i++) {
      cout << array_of_elements[i] << " ";
    }
    cout << endl;
    cout << "number_of_elements_in_array = " << number_of_elements_in_array << endl;
    cout << "target_element = " << target_element << endl;

    int result = binary_search(array_of_elements,number_of_elements_in_array,target_element);

    if(result==-1)
      cout << "not found, result = " << result << endl;
    else
      cout << "found in position = " << result+1 << endl;


    return 0;
}

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
}