Java/Searches/IterativeBinarySearch.java at dev · primary-code-test/Java · GitHub

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package Searches;

import static java.lang.String.format;

import java.util.Arrays;

import java.util.Random;

import java.util.stream.Stream;

/**

* Binary search is one of the most popular algorithms This class represents iterative version

* {@link BinarySearch} Iterative binary search is likely to have lower constant factors because it

* doesn't involve the overhead of manipulating the call stack. But in java the recursive version

* can be optimized by the compiler to this version.

* <p>Worst-case performance O(log n) Best-case performance O(1) Average performance O(log n)

* Worst-case space complexity O(1)

* @author Gabriele La Greca : https://github.com/thegabriele97

* @author Podshivalov Nikita (https://github.com/nikitap492)

* @see SearchAlgorithm

* @see BinarySearch

public final class IterativeBinarySearch implements SearchAlgorithm {

/**

* This method implements an iterative version of binary search algorithm

* @param array a sorted array

* @param key the key to search in array

* @return the index of key in the array or -1 if not found

@Override

public <T extends Comparable<T>> int find(T[] array, T key) {

int l, r, k, cmp;

l = 0;

r = array.length - 1;

while (l <= r) {

k = (l + r) >>> 1;

cmp = key.compareTo(array[k]);

if (cmp == 0) {

return k;

} else if (cmp < 0) {

r = --k;

} else {

l = ++k;

}

return -1;

}

// Only a main method for test purpose

public static void main(String[] args) {

Random r = new Random();

int size = 100;

int maxElement = 100000;

Integer[] integers =

Stream.generate(() -> r.nextInt(maxElement)).limit(size).sorted().toArray(Integer[]::new);

// the element that should be found

Integer shouldBeFound = integers[r.nextInt(size - 1)];

IterativeBinarySearch search = new IterativeBinarySearch();

int atIndex = search.find(integers, shouldBeFound);

System.out.println(

String.format(

"Should be found: %d. Found %d at index %d. An array length %d",

shouldBeFound, integers[atIndex], atIndex, size));

int toCheck = Arrays.binarySearch(integers, shouldBeFound);

System.out.println(

format(

"Found by system method at an index: %d. Is equal: %b", toCheck, toCheck == atIndex));

}

Java/Searches/IterativeBinarySearch.java at dev · primary-code-test/Java · GitHub

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