Java BigInteger Calculate getNextLexicographicalPermutation(BigInteger v)

Description

It computes lexicographically the next permutation of the bits in the given number.

License

Open Source License

Parameter

Parameter	Description
v	Source number

Return

Bit-twiddled number

Declaration

public static BigInteger getNextLexicographicalPermutation(BigInteger v) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.math.BigInteger;

public class Main {
    /**/*  ww w .j  av a 2  s.  c  o m*/
     * It computes lexicographically the next permutation of the bits in the given number.
     *
     * For example 3 = 0b000011<br>
     * - next: 0b000101 (5)<br>
     * - next: 0b000110 (6)<br>
     * - next: 0b001001 (9)<br>
     * - next: 0b001010 (10)<br>
     * - next: 0b001100 (12)<br>
     * - next: 0b010001 (17)<br>
     *
     * Copied from <a href="http://graphics.stanford.edu/~seander/bithacks.html#NextBitPermutation">Bit Twiddling Hacks: Compute the lexicographically next bit permutation</a>
     * @param v    Source number
     * @return  Bit-twiddled number
     */
    public static long getNextLexicographicalPermutation(long v) {
        long t = (v | (v - 1)) + 1;
        return t | ((((t & -t) / (v & -v)) >> 1) - 1);
    }

    /**
     * It computes lexicographically the next permutation of the bits in the given number.
     *
     * For example 3 = 0b000011<br>
     * - next: 0b000101 (5)<br>
     * - next: 0b000110 (6)<br>
     * - next: 0b001001 (9)<br>
     * - next: 0b001010 (10)<br>
     * - next: 0b001100 (12)<br>
     * - next: 0b010001 (17)<br>
     *
     * Copied from <a href="http://graphics.stanford.edu/~seander/bithacks.html#NextBitPermutation">Bit Twiddling Hacks: Compute the lexicographically next bit permutation</a>
     * @param v    Source number
     * @return  Bit-twiddled number
     */
    public static BigInteger getNextLexicographicalPermutation(BigInteger v) {
        BigInteger t = v.or(v.subtract(BigInteger.ONE)).add(BigInteger.ONE);
        return t.and(t.negate()).divide(v.and(v.negate())).shiftRight(1)
                .subtract(BigInteger.ONE).or(t);
    }
}

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