Java Unsigned Number Create unsignedBinarySearch(final short[] array, final int begin, final int end, final short k)

Description

Look for value k in array in the range [begin,end).

License

Apache License

Parameter

Parameter	Description
array	array where we search
begin	first index (inclusive)
end	last index (exclusive)
k	value we search for

Return

count

Declaration

public static int unsignedBinarySearch(final short[] array, final int begin, final int end, final short k) 

Method Source Code

//package com.java2s;
/*/*from   w  w  w .ja v  a 2  s.com*/
 * (c) the authors Licensed under the Apache License, Version 2.0.
 */

public class Main {
    /**
     * optimization flag: whether to use hybrid binary search: hybrid formats
     * combine a binary search with a sequential search
     */
    public static boolean USE_HYBRID_BINSEARCH = true;

    /**
     * Look for value k in array in the range [begin,end). If the value is found, return its index. If
     * not, return -(i+1) where i is the index where the value would be inserted. The array is assumed
     * to contain sorted values where shorts are interpreted as unsigned integers.
     * 
     * @param array array where we search
     * @param begin first index (inclusive)
     * @param end last index (exclusive)
     * @param k value we search for
     * @return count
     */
    public static int unsignedBinarySearch(final short[] array, final int begin, final int end, final short k) {
        if (USE_HYBRID_BINSEARCH) {
            return hybridUnsignedBinarySearch(array, begin, end, k);
        } else {
            return branchyUnsignedBinarySearch(array, begin, end, k);
        }
    }

    protected static int hybridUnsignedBinarySearch(final short[] array, final int begin, final int end,
            final short k) {
        int ikey = toIntUnsigned(k);
        // next line accelerates the possibly common case where the value would
        // be inserted at the end
        if ((end > 0) && (toIntUnsigned(array[end - 1]) < ikey)) {
            return -end - 1;
        }
        int low = begin;
        int high = end - 1;
        // 32 in the next line matches the size of a cache line
        while (low + 32 <= high) {
            final int middleIndex = (low + high) >>> 1;
            final int middleValue = toIntUnsigned(array[middleIndex]);

            if (middleValue < ikey) {
                low = middleIndex + 1;
            } else if (middleValue > ikey) {
                high = middleIndex - 1;
            } else {
                return middleIndex;
            }
        }
        // we finish the job with a sequential search
        int x = low;
        for (; x <= high; ++x) {
            final int val = toIntUnsigned(array[x]);
            if (val >= ikey) {
                if (val == ikey) {
                    return x;
                }
                break;
            }
        }
        return -(x + 1);
    }

    protected static int branchyUnsignedBinarySearch(final short[] array, final int begin, final int end,
            final short k) {
        int ikey = toIntUnsigned(k);
        // next line accelerates the possibly common case where the value would
        // be inserted at the end
        if ((end > 0) && (toIntUnsigned(array[end - 1]) < ikey)) {
            return -end - 1;
        }
        int low = begin;
        int high = end - 1;
        while (low <= high) {
            final int middleIndex = (low + high) >>> 1;
            final int middleValue = toIntUnsigned(array[middleIndex]);

            if (middleValue < ikey) {
                low = middleIndex + 1;
            } else if (middleValue > ikey) {
                high = middleIndex - 1;
            } else {
                return middleIndex;
            }
        }
        return -(low + 1);
    }

    protected static int toIntUnsigned(short x) {
        return x & 0xFFFF;
    }
}

Related

1. unsigned8(byte b)
2. unsigned_byte(byte b)
3. unsignedAddOverflow(int operand1, int operand2)
4. unsignedArrayCompareLex(byte[] a, byte[] b)
5. unsignedArrayCompareLex(char[] a, char[] b)
6. unsignedByte(int b)
7. unsignedByteFromInt(int i)
8. unsignedBytesToInts(Byte[] bytes)
9. unsignedByteToInt(byte b)