80 lines
2.4 KiB
Java
80 lines
2.4 KiB
Java
package Searches;
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import java.util.Arrays;
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import java.util.Random;
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import java.util.stream.Stream;
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import static java.lang.String.format;
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/**
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* Binary search is one of the most popular algorithms
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* This class represents iterative version {@link BinarySearch}
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* Iterative binary search is likely to have lower constant factors because it doesn't involve the overhead of manipulating the call stack.
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* But in java the recursive version can be optimized by the compiler to this version.
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* <p>
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* Worst-case performance O(log n)
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* Best-case performance O(1)
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* Average performance O(log n)
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* Worst-case space complexity O(1)
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*
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* @author Gabriele La Greca : https://github.com/thegabriele97
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* @author Podshivalov Nikita (https://github.com/nikitap492)
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* @see SearchAlgorithm
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* @see BinarySearch
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*/
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public final class IterativeBinarySearch implements SearchAlgorithm {
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/**
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* This method implements an iterative version of binary search algorithm
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*
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* @param array a sorted array
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* @param key the key to search in array
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* @return the index of key in the array or -1 if not found
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*/
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@Override
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public <T extends Comparable<T>> int find(T[] array, T key) {
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int l, r, k, cmp;
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l = 0;
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r = array.length - 1;
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while (l <= r) {
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k = (l + r) >>> 1;
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cmp = key.compareTo(array[k]);
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if (cmp == 0) {
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return k;
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} else if (cmp < 0) {
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r = --k;
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} else {
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l = ++k;
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}
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}
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return -1;
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}
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//Only a main method for test purpose
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public static void main(String[] args) {
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Random r = new Random();
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int size = 100;
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int maxElement = 100000;
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Integer[] integers = Stream.generate(() -> r.nextInt(maxElement)).limit(size).sorted().toArray(Integer[]::new);
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//the element that should be found
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Integer shouldBeFound = integers[r.nextInt(size - 1)];
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IterativeBinarySearch search = new IterativeBinarySearch();
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int atIndex = search.find(integers, shouldBeFound);
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System.out.println(String.format("Should be found: %d. Found %d at index %d. An array length %d"
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, shouldBeFound, integers[atIndex], atIndex, size));
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int toCheck = Arrays.binarySearch(integers, shouldBeFound);
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System.out.println(format("Found by system method at an index: %d. Is equal: %b", toCheck, toCheck == atIndex));
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}
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}
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