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BinarySearch.java
78 lines (66 loc) · 1.99 KB
/
BinarySearch.java
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package com.yunikov.algorithms.search;
import java.util.Arrays;
import java.util.Optional;
/**
* Implementation of <a href="https://en.wikipedia.org/wiki/Binary_search_algorithm">binary search algorithm in array</a>
*/
public class BinarySearch extends ArraySearch {
/**
* {@inheritDoc}
*/
@Override
public Optional<Integer> searchSorted(final int[] array, final int key) {
int from = 0;
int to = array.length - 1;
while (from <= to) {
final int mid = (from + to) >>> 1; // equivalent to dividing by 2
final long midVal = array[mid];
if (midVal < key) {
from = mid + 1;
} else if (midVal > key) {
to = mid - 1;
} else {
return Optional.of(mid);
}
}
return Optional.empty();
}
/**
* {@inheritDoc}
*/
@Override
public Optional<Long> searchSorted(final long[] array, final long key) {
long from = 0;
long to = array.length - 1;
while (from <= to) {
final long mid = ((from + to) >>> 1); // equivalent to dividing by 2
final long midVal = array[((int) mid)];
if (midVal < key) {
from = mid + 1;
} else if (midVal > key) {
to = mid - 1;
} else {
return Optional.of(mid);
}
}
return Optional.empty();
}
/**
* {@inheritDoc}
*/
@Override
public Optional<Integer> search(final int[] array, final int key) {
final int[] arrayCopy = Arrays.copyOf(array, array.length);
Arrays.sort(arrayCopy);
return searchSorted(arrayCopy, key);
}
/**
* {@inheritDoc}
*/
@Override
public Optional<Long> search(final long[] array, final long key) {
final long[] arrayCopy = Arrays.copyOf(array, array.length);
Arrays.sort(arrayCopy);
return searchSorted(arrayCopy, key);
}
}