/*license*\
XBN-Java: Copyright (C) 2014, Jeff Epstein (aliteralmind __DASH__ github __AT__ yahoo __DOT__ com)
This software is dual-licensed under the:
- Lesser General Public License (LGPL) version 3.0 or, at your option, any later version;
- Apache Software License (ASL) version 2.0.
Either license may be applied at your discretion. More information may be found at
- http://en.wikipedia.org/wiki/Multi-licensing.
The text of both licenses is available in the root directory of this project, under the names "LICENSE_lgpl-3.0.txt" and "LICENSE_asl-2.0.txt". The latest copies may be downloaded at:
- LGPL 3.0: https://www.gnu.org/licenses/lgpl-3.0.txt
- ASL 2.0: http://www.apache.org/licenses/LICENSE-2.0.txt
\*license*/
package com.github.xbn.examples.util.non_xbn;
/**
<p>Given a 31-bit binary-int, as a string (representing an int with zero or more bit-flags, where the most-significant-bit, the "sign bit", is removed), get the <i>inverted</i> index of the first one-bit (if the left-most bit is a 1, 31 is the result).</p>
<p>{@code java com.github.xbn.examples.util.non_xbn.TwoExponentHighestOneBitUsingBinaryStrings}</p>
* @since 0.1.0
* @author Copyright (C) 2014, Jeff Epstein ({@code aliteralmind __DASH__ github __AT__ yahoo __DOT__ com}), dual-licensed under the LGPL (version 3.0 or later) or the ASL (version 2.0). See source code for details. <a href="http://xbnjava.aliteralmind.com">{@code http://xbnjava.aliteralmind.com}</a>, <a href="https://github.com/aliteralmind/xbnjava">{@code https://github.com/aliteralmind/xbnjava}</a>
**/
public class TwoExponentHighestOneBitUsingBinaryStrings {
public static final void main(String[] ignored) {
//One bit
test("1000000000000000000000000000000"); //VALUE_OF_31ST_ONE_BIT
test("0000100000000000000000000000000");
test("0000000000000000000000000000010");
test("0000000000000000000000000000000");
//Two
test("0110000000000000000000000000000");
test("0000000000000000000000000000011");
}
private static final void test(String int_binStr) {
int i = Integer.parseInt(int_binStr, 2);
System.out.println("31-bits: " + int_binStr + ", int: " + i);
int exponent = getInvertedIndexHighestOneBit(int_binStr);
System.out.println(" Highest one-bit is two-to-the-exponent-of: " + exponent);
if(exponent != -1) {
exponent = getInvertedIndexHighestOneBit(int_binStr, (exponent - 1));
System.out.println(" Next-highest one-bit is two-to-the-exponent-of: " + exponent);
}
System.out.println();
}
public static final int getInvertedIndexHighestOneBit(String all31Bits_zeroPadded) {
return getInvertedIndexHighestOneBit(all31Bits_zeroPadded, 30);
}
public static final int getInvertedIndexHighestOneBit(String all31Bits_zeroPadded, int inverted_startIdx) {
int idxFirstOneBit = all31Bits_zeroPadded.indexOf("1", (30 - inverted_startIdx));
if(idxFirstOneBit == -1) {
return -1;
}
return (30 - idxFirstOneBit);
}
}