mindol1004/spring-boot-rest
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Powerset (#8475)

Browse Source 
* PowerSet generation is Java and respective unit tests are added

* function name is adjusted to the actual ordering name (Reverse Lexicographical ordering)

* Guava example test function is changed

* LazyLoad powerSet (based on Guava implementation) is added

* set is used instead of map.keySet()

* Lexicographic Order and Gray Order are removed from function names. Unused function (rank and unrank), which are not used in the text, are removed
This commit is contained in:
mnafshin
2020-01-06 01:01:27 +03:30
committed by maibin
parent 0d94a27f9d
commit 3b3880a942
2 changed files with 5 additions and 59 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
core-java-modules/core-java-lang-math/src/main/java/com/baeldung/powerset/PowerSetUtility.java
View File

@@ -1,7 +1,5 @@
package com.baeldung.powerset;
import com.google.common.collect.Sets;
import javax.annotation.Nullable;
import java.util.AbstractSet;
import java.util.ArrayList;
@@ -163,7 +161,7 @@ public class PowerSetUtility<T> {
return unMapIndex(powerSetIndices);
}
private List<List<Boolean>> iterativePowerSetByLoopOverNumbersWithReverseLexicographicalOrder(int n) {
private List<List<Boolean>> iterativePowerSetByLoopOverNumbers(int n) {
List<List<Boolean>> powerSet = new ArrayList<>();
for (int i = 0; i < (1 << n); i++) {
List<Boolean> subset = new ArrayList<>(n);
@@ -174,7 +172,7 @@ public class PowerSetUtility<T> {
return powerSet;
}
private List<List<Boolean>> iterativePowerSetByLoopOverNumbersWithGrayCodeOrder(int n) {
private List<List<Boolean>> iterativePowerSetByLoopOverNumbersWithMinimalChange(int n) {
List<List<Boolean>> powerSet = new ArrayList<>();
for (int i = 0; i < (1 << n); i++) {
List<Boolean> subset = new ArrayList<>(n);
@@ -195,32 +193,16 @@ public class PowerSetUtility<T> {
public List<List<T>> iterativePowerSetByLoopOverNumbers(Set<T> set) {
initializeMap(set);
List<List<Boolean>> sets = iterativePowerSetByLoopOverNumbersWithReverseLexicographicalOrder(set.size());
List<List<Boolean>> sets = iterativePowerSetByLoopOverNumbers(set.size());
return unMapListBinary(sets);
}
public List<List<T>> iterativePowerSetByLoopOverNumbersMinimalChange(Set<T> set) {
initializeMap(set);
List<List<Boolean>> sets = iterativePowerSetByLoopOverNumbersWithGrayCodeOrder(set.size());
List<List<Boolean>> sets = iterativePowerSetByLoopOverNumbersWithMinimalChange(set.size());
return unMapListBinary(sets);
}
public static int getRankInLexicographicalOrder(List<Boolean> subset) {
int rank = 0;
for (int i = 0; i < subset.size(); i++)
if (subset.get(i))
rank += (1 << (subset.size() - i - 1));
return rank;
}
public static List<Boolean> getSubsetForRankInLexicographicalOrder(int rank, int sizeOfSet) {
Boolean[] subset = new Boolean[sizeOfSet];
for(int j = 0; j < sizeOfSet; j++) {
subset[sizeOfSet - j - 1] = ((rank & (1 << j)) > 0);
}
return Arrays.asList(subset);
}
private Set<Set<Integer>> recursivePowerSetIndexRepresentation(int idx, int n) {
if (idx == n) {
Set<Set<Integer>> empty = new HashSet<>();