Check out example codes for "binary search program c++". It will help you in understanding the concepts better.

Code Example 1

``````// C program to implement recursive Binary Search
#include <stdio.h>

// A recursive binary search function. It returns
// location of x in given array arr[l..r] is present,
// otherwise -1
int binarySearch(int arr[], int l, int r, int x)
{
if (r >= l) {
int mid = l + (r - l) / 2;

// If the element is present at the middle
// itself
if (arr[mid] == x)
return mid;

// If element is smaller than mid, then
// it can only be present in left subarray
if (arr[mid] > x)
return binarySearch(arr, l, mid - 1, x);

// Else the element can only be present
// in right subarray
return binarySearch(arr, mid + 1, r, x);
}

// We reach here when element is not
// present in array
return -1;
}

int main(void)
{
int arr[] = { 2, 3, 4, 10, 40 };
int n = sizeof(arr) / sizeof(arr[0]);
int x = 10;
int result = binarySearch(arr, 0, n - 1, x);
(result == -1) ? printf("Element is not present in array")
: printf("Element is present at index %d",
result);
return 0;
}``````

Code Example 2

``````#include <iostream>
using namespace std;

// This program performs a binary search through an array, must be sorted to work
int binarySearch(int array[], int size, int value)
{
int first = 0,             // First array element
last = size - 1,       // Last array element
middle,                // Mid point of search
position = -1;         // Position of search value
bool found = false;        // Flag
while (!found && first <= last)   {
middle = (first + last) / 2;     // Calculate mid point
if (array[middle] == value)      // If value is found at mid
{
found = true;
position = middle;
}
else if (array[middle] > value)  // If value is in lower half
last = middle - 1;
else
first = middle + 1;          // If value is in upper half
}
return position;
}
int main (){
const int size = 5; // size initialization
int array[size] = {1, 2, 3, 4, 5}; // declare array of size 10
int value; // declare value to be searched for
int result; // declare variable that will be returned after binary search

cout << "What value would you like to search for? "; // prompt user to enter value
cin >> value;
result = binarySearch(array, size, value);

if (result == -1) // if value isn't found display this message
else { // If value is found, displays message
cout << "Your value is in the array.\n";
}
return 0;
}``````

Code Example 3

``````def binarySearch(arr, l, r, x):

while l <= r:

mid = l + (r - l) // 2;

# Check if x is present at mid
if arr[mid] == x:
return mid

# If x is greater, ignore left half
elif arr[mid] < x:
l = mid + 1

# If x is smaller, ignore right half
else:
r = mid - 1

# If we reach here, then the element
# was not present
return -1

# Driver Code
arr = [ 2, 3, 4, 10, 40 ]
x = 10

# Function call
result = binarySearch(arr, 0, len(arr)-1, x)

if result != -1:
print ("Element is present at index % d" % result)
else:
print ("Element is not present in array")``````

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