what is binary search code example

Example 1: binary search program c++

#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
        cout << "Not found\n";
    else  // If value is found, displays message
        cout << "Your value is in the array.\n"; 
  
    return 0;
}

Example 2: binary search java

// Java implementation of iterative Binary Search 
class BinarySearch { 
	// Returns index of x if it is present in arr[], 
	// else return -1 
	int binarySearch(int arr[], int x) 
	{ 
		int l = 0, r = arr.length - 1; 
		while (l <= r) { 
			int m = l + (r - l) / 2; 

			// Check if x is present at mid 
			if (arr[m] == x) 
				return m; 

			// If x greater, ignore left half 
			if (arr[m] < x) 
				l = m + 1; 

			// If x is smaller, ignore right half 
			else
				r = m - 1; 
		} 

		// if we reach here, then element was 
		// not present 
		return -1; 
	} 

	// Driver method to test above 
	public static void main(String args[]) 
	{ 
		BinarySearch ob = new BinarySearch(); 
		int arr[] = { 2, 3, 4, 10, 40 }; 
		int n = arr.length; 
		int x = 10; 
		int result = ob.binarySearch(arr, x); 
		if (result == -1) 
			System.out.println("Element not present"); 
		else
			System.out.println("Element found at "
							+ "index " + result); 
	} 
}

Example 3: binary search in c

//C Implementation
#include<stdio.h>
int BinarySearch(int arr[], int search, int mid, int len){
    if(mid == -1 || mid == len+1){
        printf("\nSearched Element doesn't exist.");
        return 1;
    }
    else if (search > arr[mid]){
        mid++;
        BinarySearch(arr,search,mid,len);
        return 0;
    }
    else if (search < arr[mid]){
        mid--;
        BinarySearch(arr,search,mid,len);
        return 0;
    }
    else if(search == arr[mid]) {
        printf("\n Searched Element found at Location %d.",mid);
        return 1;
    } 
}
void main(){
    int arr[] = {1,2,3,4,5,6,7,8,9};
    int len = sizeof(arr) / sizeof(int);
    int mid = (int) (len / 2) + 1;
    printf("\n Please Enter Number You Want to Search \n >  ");
    int search;
    scanf("%d",&search);
    int Result = BinarySearch(arr,search,mid,len);
}

Example 4: binary search

import java.util.Scanner;

public class Binarysearch {

	public static void main(String[] args) {
		int[] x= {1,2,3,4,5,6,7,8,9,10,16,18,20,21};
		Scanner scan=new Scanner(System.in);
		System.out.println("enter the key:");
		int key=scan.nextInt();
		int flag=0;
		int low=0;
		int high=x.length-1;
		int mid=0;
		while(low<=high)
		{
			mid=(low+high)/2;
			if(key<x[mid])
			{
				high=mid-1;
			}
			else if(key>x[mid])
			{
				low=mid+1;
			}
			else if(key==x[mid])
			{
				flag++;
				System.out.println("found at index:"+mid);
				break;
			}
		}
		if(flag==0)
		{
			System.out.println("Not found");
		}
		

	}

}

Example 5: binary search

//it is using divide and conquer method
#include <iostream>

using namespace std;
void binarysearch(int arr[],int start,int end,int val)
{
    if(start<end)
    {
        int mid=(start+end)/2;
        if(arr[mid]==val)
        {
            cout<<"value found:"<<endl;
        }
        else if(arr[mid]<val)
        {
            binarysearch(arr,mid+1,end,val);
        }
        else if(arr[mid]>val)
        {
            binarysearch(arr,start,mid-1,val);
        }
    }
    else
    {
        cout<<"not present:"<<endl;
    }
}

int main()
{
    int n;
    cout<<"enter the size of the array:"<<endl;
    cin>>n;
    int arr[n];
    cout<<"enter the elements of the array:"<<endl;
    for(int i=0;i<n;i++)
    {
        cin>>arr[i];
    }
    cout<<"enter the value you want to search:"<<endl;
    int val;
    cin>>val;
    binarysearch(arr,0,n-1,val);

    return 0;
}

Example 6: Implement a binary search of a sorted array of integers Using pseudo-code.

# Here's the pseudocode for binary search, modified for searching in an array. The inputs are the array, which we call array; the number n of elements in array; and target, the number being searched for. The output is the index in array of target:

    1.Let min = 0 and max = n-1.
    2. Compute guess as the average of max and min, rounded down (so that it is an integer).
    3. If array[guess] equals target, then stop. You found it! Return guess.
    4. If the guess was too low, that is, array[guess] < target, then set min = guess + 1.
    5. Otherwise, the guess was too high. Set max = guess - 1.
    6. Go back to step 2.