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La ricerca binaria viene utilizzata per cercare un elemento chiave tra più elementi. La ricerca binaria è più veloce della ricerca lineare.

java switch int

In caso di ricerca binaria, gli elementi dell'array devono essere in ordine crescente. Se hai un array non ordinato, puoi ordinare l'array utilizzando Array.sort(arr) metodo.

Esempio di ricerca binaria in Java

Vediamo un esempio di ricerca binaria in Java.

 class BinarySearchExample{ public static void binarySearch(int arr[], int first, int last, int key){ int mid = (first + last)/2; while( first <= last ){ if ( arr[mid] system.out.println('element is not found!'); } public static void main(string args[]){ int arr[]="{10,20,30,40,50};" key="30;" binarysearch(arr,0,last,key); < pre> <span> Test it Now </span> <p>Output:</p> <pre> Element is found at index: 2 </pre> <h2>Binary Search Example in Java using Recursion</h2> <p>Let&apos;s see an example of binary search in java where we are going to search an element from an array using recursion.</p> <pre> class BinarySearchExample1{ public static int binarySearch(int arr[], int first, int last, int key){ if (last&gt;=first){ int mid = first + (last - first)/2; if (arr[mid] == key){ return mid; } if (arr[mid] &gt; key){ return binarySearch(arr, first, mid-1, key);//search in left subarray }else{ return binarySearch(arr, mid+1, last, key);//search in right subarray } } return -1; } public static void main(String args[]){ int arr[] = {10,20,30,40,50}; int key = 30; int last=arr.length-1; int result = binarySearch(arr,0,last,key); if (result == -1) System.out.println(&apos;Element is not found!&apos;); else System.out.println(&apos;Element is found at index: &apos;+result); } } </pre> <span> Test it Now </span> <p>Output:</p> <pre> Element is found at index: 2 </pre> <h2>Binary Search Example in Java using Arrays.binarySearch()</h2> <pre> import java.util.Arrays; class BinarySearchExample2{ public static void main(String args[]){ int arr[] = {10,20,30,40,50}; int key = 30; int result = Arrays.binarySearch(arr,key); if (result <0) system.out.println('element is not found!'); else found at index: '+result); } < pre> <span> Test it Now </span> <p>Output:</p> <pre> Element is found at index: 2 </pre></0)></pre></=>

Esempio di ricerca binaria in Java utilizzando la ricorsione

Vediamo un esempio di ricerca binaria in Java in cui cercheremo un elemento da un array utilizzando la ricorsione.

 class BinarySearchExample1{ public static int binarySearch(int arr[], int first, int last, int key){ if (last>=first){ int mid = first + (last - first)/2; if (arr[mid] == key){ return mid; } if (arr[mid] > key){ return binarySearch(arr, first, mid-1, key);//search in left subarray }else{ return binarySearch(arr, mid+1, last, key);//search in right subarray } } return -1; } public static void main(String args[]){ int arr[] = {10,20,30,40,50}; int key = 30; int last=arr.length-1; int result = binarySearch(arr,0,last,key); if (result == -1) System.out.println('Element is not found!'); else System.out.println('Element is found at index: '+result); } } 

Produzione:

 Element is found at index: 2 

Esempio di ricerca binaria in Java utilizzando Arrays.binarySearch()

 import java.util.Arrays; class BinarySearchExample2{ public static void main(String args[]){ int arr[] = {10,20,30,40,50}; int key = 30; int result = Arrays.binarySearch(arr,key); if (result <0) system.out.println(\'element is not found!\'); else found at index: \'+result); } < pre> <span> Test it Now </span> <p>Output:</p> <pre> Element is found at index: 2 </pre></0)>