Alachisoft.NCache.Common.SearchAlgorithms.BinarySearch Maven / Gradle / Ivy

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/*
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 * and open the template in the editor.
 */
package Alachisoft.NCache.Common.SearchAlgorithms;

import java.util.Comparator;
import java.util.List;

/**
 * @author Basit Anwer
 */
public class BinarySearch {
    public static void insertItem(List _link, Object o, Comparator comp) {

        if (comp != null) {
        } else {
            throw new IllegalArgumentException("Value cannot be null."+System.lineSeparator()+"Parameter name: comparator");
        }

        if (_link.size() == 0) {
            _link.add(o);
            return;
        }

        boolean insert = false;
        int itemNumber = _link.size() / 2;
        int less = 0;
        int greater = _link.size() - 1;

        while (!insert) {

            Object key = _link.get(itemNumber);
            if (comp.compare(o, key) < 0) //Less than
            {
                if ((itemNumber - less) == 1) {
                    greater = itemNumber = less;
                    continue;
                } else if (itemNumber == less) {
                    _link.add(itemNumber, o);
                    insert = true;
                    break;
                }

                greater = itemNumber;
                itemNumber = (itemNumber - less) / 2 + less;
            } else if (comp.compare(o, key) > 0) //Greater than
            {
                if ((greater - itemNumber) == 1) {
                    less = itemNumber = greater;
                    continue;
                } else if (itemNumber == greater) {
                    _link.add(itemNumber + 1, o);
                    insert = true;
                    break;
                }

                less = itemNumber;
                itemNumber = (greater - itemNumber) / 2 + itemNumber;
            } else {
                throw new IllegalArgumentException("Duplicate Key found");
            }
        }

    }


    /**
     * Searches item using Binary Search algorithm, returns Index of item
     *
     * @param _link    List of sorted array
     * @param findItem Item to find
     * @param comp     Comparator
     * @return -1 if not found, else returns the index number
     */
    public static int searchItem(List _link, Object findItem, Comparator comp) {
        if (comp != null) {
        } else {
            throw new IllegalArgumentException("Value cannot be null."+System.lineSeparator()+"Parameter name: Comparator");
        }

        if (_link.size() == 0) {
            return -1;
        }

        boolean insert = false;
        int itemNumber = _link.size() / 2;
        int less = 0;
        int greater = _link.size() - 1;

        while (!insert) {

            Object key = _link.get(itemNumber);

            if (comp.compare(findItem, key) < 0) //Less than
            {
                if ((itemNumber - less) == 1) {
                    greater = itemNumber = less;
                    continue;
                } else if (itemNumber == less) {
                    insert = true;
                    break;
                }

                greater = itemNumber;
                itemNumber = (itemNumber - less) / 2 + less;
            } else if (comp.compare(findItem, key) > 0) //Greater than
            {
                if ((greater - itemNumber) == 1) {
                    less = itemNumber = greater;
                    continue;
                } else if (itemNumber == greater) {
                    insert = true;
                    break;
                }

                less = itemNumber;
                itemNumber = (greater - itemNumber) / 2 + itemNumber;
            } else {
                return itemNumber;
            }
        }

        //Not found
        return -1;
    }
}