Binary Search In C++

beg = 0;
end = size - 1;
while ( beg <= end)
{
// calculate mid value
mid = (beg + end) / 2;
/* if the specified element is found at mid index, terminate the process and return the index. */
// Check middle element is equal to the defined element.
If (aarr[mid] == num)
{
return mid + 1;
}
else if (arr[mid] > num)
{
	End = mid - 1;
}
Else if (arr [mid] < num)
{
	Beg = mid + 1;
}
}
// If the element does not exist in the array, return -1.
Return -1;

#include <iostream>
#include <conio.h>
using namespace std;
int main ()
{
	// declaration of the variables and array
	int arr[100], st, mid, end, i, num, tgt;
	
	cout << " Define the size of the array: " << endl;
	cin >> num; // get size
	
	// enter only sorted array
        cout << " Enter the values in sorted array either ascending or descending order: " << endl;
	// use for loop to iterate values
	for (i = 0; i < num; i++)
	{
		cout << " arr [" << i << "] = ";
		cin >> arr[i];
	}
	
	// initialize the starting and ending variable's values
	st = 0;
	end = num - 1; // size of array (num) - 1
	
	// define the item or value to be search
	cout << " Define a value to be searched from sorted array: " << endl;
	cin >> tgt;
	
	// use while loop to check 'st', should be less than equal to 'end'.
	while ( st <= end)
	{
		// get middle value by splitting into half
		mid = ( st + end ) / 2;
		/* if we get the target value at mid index, print the position and exit from the program. */
		if (arr[mid] == tgt)
		{
			cout << " Element is found at index " << (mid + 1);
			exit (0); // use for exit program the program
		}
		// check the value of target element is greater than the mid element' value
		else if ( tgt > arr[mid])
		{
			st = mid + 1; // set the new value for st variable
		}
		
		// check the value of target element is less than the mid element' value
		else if ( tgt < arr[mid])
		{
			end = mid - 1; // set the new value for end variable
		}
	}
	cout << " Number is not found. " << endl;
	return 0;
}

Define the size of the array: 
10
Enter the values in sorted array either ascending or descending order:
Arr [0]  = 12
Arr [1]  = 24
Arr [2]  = 36
Arr [3]  = 48
Arr [4]  = 50
Arr [5]  = 54
Arr [6]  = 58
Arr [7]  = 60
Arr [8]  = 72
Arr [9]  = 84
Define a value to be searched from sorted array:
50
Element is found at index 5

/* program to find the specified element from the sorted array using the binary search in C++. */
#include <iostream>
using namespace std;
/* create user-defined function and pass different parameters:
arr[] - it represents the sorted array;
num variable represents the size of an array;
tgt variable represents the target or specified variable to be searched in the sorted array. */
int bin_search (int arr[], int num, int tgt)
{
	int beg = 0, end = num - 1;
	// use loop to check all sorted elements
	while (beg <= end)
	{
		/* get the mid value of sorted array and then compares with target element. */
		int mid = (beg + end) /2;		
		if (tgt == arr[mid])
		{
			return mid; // when mid is equal to tgt value
		}		
		// check tgt is less than mid value, discard left element
		else if (tgt < arr[mid])
		{
			end = mid - 1;
		}		
		// if the target is greater than the mid value, discard all elements
		else {
			beg = mid + 1;
		}
	}
	// return -1 when target is not exists in the array
	return -1;
}
int main ()
{
	// declaration of the arrays
	int arr[] = { 5, 10, 15, 20, 25, 30, 37, 40};
	int tgt = 25; // specified the target element	
	int num = sizeof (arr) / sizeof (arr[0]);
	// declare pos variable to get the position of the specified element
	int pos = bin_search (arr, num, tgt);	
	if (pos != 1)
	{
		cout << " Element is found at position " << (pos + 1)<< endl;
	}
	else
	{
		cout << " Element is not found in the array" << endl;
	}
	return 0;
}

Element is found at position 5

/* find the specified number using the binary search technique inside the recursion method. */
#include <iostream>
using namespace std;
// define a function
int binary_search (int [], int, int, int);
int main ()
{
	// declaration of the variables
	int i, arr[100], tgt, num, ind, st, end;
	cout << " Define the size of an array: ";
	cin >> num;	
	cout << " Enter " << num << " elements in ascending order: " << endl;
	// use for loop to ieterate the number
	for ( i = 0; i < num; i++)
	{
		cout << " arr [" << i << "] = ";
		cin >> arr[i];
	}
	// define the element to be search
	cout << " \n Enter an element to be searched in ascending array: ";
	cin >> tgt;	
	// ind define the index number
	ind = binary_search (arr, 0, num - 1, tgt);	
	// check for existemce of the specified element
	if (ind == 0)
		cout << tgt << " is not available in the array-list";	
	else
		cout << tgt << " is available at position " << ind << endl;
	return 0;
}
// function defnition
int binary_search (int arr[], int st, int end, int tgt)
{
	int mid;
	// check st is greater than end
	if (st > end)
	{
		return 0;
	}
	mid = (st + end) / 2; // get middle value of the sorted array
	
	// check middle value is equal to target number
	if (arr[mid] == tgt)
	{
		return (mid + 1);
	}
	// check mid is greater than target number
	else if (arr[mid] > tgt)
	{
		binary_search (arr, st, mid - 1, tgt);
	}
	// check mid is less than target number
	else if (arr [mid] < tgt)
	{
		binary_search (arr, mid + 1, end, tgt);
	}
}

Define the size of an array: 10
Arr [0] = 2
Arr [1] = 4
Arr [2] = 5
Arr [3] = 8
Arr [4] = 12
Arr [5] = 13
Arr [6] = 27
Arr [7] = 36
Arr [8] = 49
Arr [9] = 51

Enter an element to be searched in ascending array: 12
12 is available at position 6.