binary search in java

1#include <iostream>
2using namespace std;
3
4// This program performs a binary search through an array, must be sorted to work
5int binarySearch(int array[], int size, int value) 
6{   
7    int first = 0,         // First array element       
8    last = size - 1,       // Last array element       
9    middle,                // Mid point of search       
10    position = -1;         // Position of search value   
11    bool found = false;        // Flag   
12    while (!found && first <= last) 
13    {      
14        middle = (first + last) / 2;     // Calculate mid point      
15        if (array[middle] == value)      // If value is found at mid      
16    	{         
17                found = true;         
18                position = middle;      
19        }      
20        else if (array[middle] > value)  // If value is in lower half         
21            last = middle - 1;      
22        else         
23            first = middle + 1;          // If value is in upper half   
24    }   
25    return position;
26}
27int main ()
28{
29    const int size = 5; // size initialization
30    int array[size] = {1, 2, 3, 4, 5}; // declare array of size 10
31    int value; // declare value to be searched for
32    int result; // declare variable that will be returned after binary search
33
34    cout << "What value would you like to search for? "; // prompt user to enter value
35    cin >> value;
36    result = binarySearch(array, size, value);
37
38    if (result == -1) // if value isn't found display this message
39        cout << "Not found\n";
40    else  // If value is found, displays message
41        cout << "Your value is in the array.\n"; 
42  
43    return 0;
44}

1// Java implementation of iterative Binary Search 
2class BinarySearch { 
3	// Returns index of x if it is present in arr[], 
4	// else return -1 
5	int binarySearch(int arr[], int x) 
6	{ 
7		int l = 0, r = arr.length - 1; 
8		while (l <= r) { 
9			int m = l + (r - l) / 2; 
10
11			// Check if x is present at mid 
12			if (arr[m] == x) 
13				return m; 
14
15			// If x greater, ignore left half 
16			if (arr[m] < x) 
17				l = m + 1; 
18
19			// If x is smaller, ignore right half 
20			else
21				r = m - 1; 
22		} 
23
24		// if we reach here, then element was 
25		// not present 
26		return -1; 
27	} 
28
29	// Driver method to test above 
30	public static void main(String args[]) 
31	{ 
32		BinarySearch ob = new BinarySearch(); 
33		int arr[] = { 2, 3, 4, 10, 40 }; 
34		int n = arr.length; 
35		int x = 10; 
36		int result = ob.binarySearch(arr, x); 
37		if (result == -1) 
38			System.out.println("Element not present"); 
39		else
40			System.out.println("Element found at "
41							+ "index " + result); 
42	} 
43} 

1public class Main{ public static void binarySearch(int arr[], int a, int b, int key){ int mid = (a + b)/2; while( a <= b ){ if ( arr[mid] < key ){ a = mid + 1; }else if ( arr[mid] == key ){ System.out.println("number is here " + mid); break; }else{ b = mid - 1; } mid = (a + b)/2; } if ( a > b ){ System.out.println("number not here"); } } public static void main(String args[]){ int arr[] = {10,20,30,40,50}; int key = 30; int b=arr.length-1; binarySearch(arr,0,b,key); } } 

1public int runBinarySearchRecursively(
2  int[] sortedArray, int key, int low, int high) {
3    int middle = (low + high) / 2;
4        
5    if (high < low) {
6        return -1;
7    }
8
9    if (key == sortedArray[middle]) {
10        return middle;
11    } else if (key < sortedArray[middle]) {
12        return runBinarySearchRecursively(
13          sortedArray, key, low, middle - 1);
14    } else {
15        return runBinarySearchRecursively(
16          sortedArray, key, middle + 1, high);
17    }
18}
19

1binary search program in java.
2public class BinarySearchExample
3{
4   public static void binarySearch(int[] arrNumbers, int start, int end, int keyElement)
5   {
6      int middle = (start + end) / 2;
7      while(start <= end)
8      {
9         if(arrNumbers[middle] < keyElement)
10         {
11            start = middle + 1;
12         }
13         else if(arrNumbers[middle] == keyElement)
14         {
15            System.out.println("Element found at index: " + middle);
16            break;
17         }
18         else
19         {
20            end = middle - 1;
21         }
22         middle = (start + end) / 2;
23      }
24      if(start > end)
25      {
26         System.out.println("Element not found!");
27      }
28   }
29   public static void main(String[] args)
30   {
31      int[] arrNumbers = {14,15,16,17,18};
32      int keyElement = 16;
33      int end = arrNumbers.length - 1;
34      binarySearch(arrNumbers, 0, end, keyElement);
35   }
36}

1import java.util.Scanner;
2
3// Binary Search in Java
4
5class Main {
6  int binarySearch(int array[], int element, int low, int high) {
7
8    // Repeat until the pointers low and high meet each other
9    while (low <= high) {
10
11      // get index of mid element
12      int mid = low + (high - low) / 2;
13
14      // if element to be searched is the mid element
15      if (array[mid] == element)
16        return mid;
17
18      // if element is less than mid element
19      // search only the left side of mid
20      if (array[mid] < element)
21        low = mid + 1;
22
23      // if element is greater than mid element
24      // search only the right side of mid
25      else
26        high = mid - 1;
27    }
28
29    return -1;
30  }
31
32  public static void main(String args[]) {
33
34    // create an object of Main class
35    Main obj = new Main();
36
37    // create a sorted array
38    int[] array = { 3, 4, 5, 6, 7, 8, 9 };
39    int n = array.length;
40
41    // get input from user for element to be searched
42    Scanner input = new Scanner(System.in);
43
44    System.out.println("Enter element to be searched:");
45
46    // element to be searched
47    int element = input.nextInt();
48    input.close();
49
50    // call the binary search method
51    // pass arguments: array, element, index of first and last element
52    int result = obj.binarySearch(array, element, 0, n - 1);
53    if (result == -1)
54      System.out.println("Not found");
55    else
56      System.out.println("Element found at index " + result);
57  }
58}