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/**
* Copyright (c) 2015, Ecole des Mines de Nantes
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the .
* 4. Neither the name of the nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY ''AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.chocosolver.graphsolver.util;
/**
* Class containing some Bit operations useful to LCA queries
*
* @author Jean-Guillaume Fages
*/
public class BitOperations {
//***********************************************************************************
// METHODS
//***********************************************************************************
// LCA typical operations
/**
* Get the lowest common ancestor of x and y in a complete binary tree
*
* @param x a node
* @param y a node
* @return the lowest common ancestor of x and y in a complete binary tree
*/
public static int binaryLCA(int x, int y) {
if (x == y) {
return x;
}
int xor = x ^ y;
int idx = getMaxExp(xor);
if (idx == -1) {
throw new UnsupportedOperationException();
}
return replaceBy1and0sFrom(x, idx);
}
/**
* @param x value/node
* @param idx index to place the 1 followed by zeroes
* @return a new int that values x until idx (excluded) and 1(000...) then
*/
public static int replaceBy1and0sFrom(int x, int idx) {
x = x >>> idx + 1;
x = x << 1;
x++;
x = x << (idx);
return x;
}
// Exponents getters
/**
* @param x a node
* @return the index of the last 1-bit, starting from 0
* 0 return -1 if no bit is set to 1
*/
public static int getMaxExp(int x) {
int exp = -1;
while (x > 0) {
exp++;
x /= 2;
}
return exp;
}
/**
* @param x node
* @param j value
* @return the index of the last 1-bit which is lower than j, starting from 0
* return -1 if no such bit exists
*/
public static int getMaxExpBefore(int x, int j) {
x %= pow(2, j);
return getMaxExp(x);
}
/**
* @param x a node
* @return the index of the first 1-bit, starting from 0
* return -1 if no such bit exists
*/
public static int getFirstExp(int x) {
if (x == 0) {
return -1;
}
int exp = 0;
while (x % 2 == 0) {
exp++;
x /= 2;
}
return exp;
}
/**
* @param x a node
* @param y a node
* @param i a value
* @return the index of the first 1-bit in both x and y, which is greater or equal to i,
* return -1 if no such bit exists
*/
public static int getFirstExpInBothXYfromI(int x, int y, int i) {
x = x >>> i;
y = y >>> i;
if ((x & y) == 0) { // x and y have no 1-bit >=i in common
return -1;
}
while (x % 2 == 0 || y % 2 == 0) {
i++;
x /= 2;
y /= 2;
}
return i;
}
// power
/**
* @param x a node
* @param pow must be >= 0
* @return x^pow
*/
public static int pow(int x, int pow) {
if (pow < 0) {
throw new UnsupportedOperationException();
}
if (pow == 0) {
return 1;
}
pow--;
int xp = x;
while (pow > 0) {
pow--;
xp *= x;
}
return xp;
}
}
