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Merge branch 'laucer-master'
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‎src/com/jwetherell/algorithms/mathematics/Permutations.java

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package com.jwetherell.algorithms.mathematics;
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import java.util.LinkedList;
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/**
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* In mathematics, the notion of permutation relates to the act of arranging all the members of a set into some sequence
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* or order, or if the set is already ordered, rearranging (reordering) its elements, a process called permuting.
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* <p>
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* http://en.wikipedia.org/wiki/Permutation
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* <br>
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* @author Justin Wetherell <phishman3579@gmail.com>
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* @author Lucjan Roslanowski <lucjanroslanowski@gmail.com>
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*/
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public class Permutations {
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/**
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* N! permutation of the characters in the string (in order)
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*/
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public static String[] permutations(String stringToGeneratePermutationsFrom) {
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final int size = numberOfPermutations(stringToGeneratePermutationsFrom.length());
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final String[] list = new String[size];
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final char[] prefix = new char[0];
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final char[] chars = stringToGeneratePermutationsFrom.toCharArray();
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permutations(list, 0, prefix, chars, 0, chars.length);
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return list;
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}
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private static final int numberOfPermutations(int N) {
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// factorial
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int result = N;
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while (N > 1)
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result *= --N;
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return result;
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}
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private static final int permutations(String[] list, int index, char[] prefix, char[] remaining, int prefixLength, int remainingLength) {
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final int N = remainingLength-prefixLength;
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if (N == 0) {
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list[index]=new String(prefix);
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index++;
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} else {
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for (int i=0; i<N; i++) {
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final char[] prefChars = new char[prefixLength+1];
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System.arraycopy(prefix, 0, prefChars, 0, prefixLength);
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System.arraycopy(remaining, i, prefChars, prefixLength, 1);
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final char[] restChars = new char[N-1];
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System.arraycopy(remaining, 0, restChars, 0, i);
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System.arraycopy(remaining, i+1, restChars, i, N-(i+1));
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index = permutations(list, index, prefChars, restChars, remainingLength-(N-1), remainingLength);
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}
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}
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return index;
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}
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/**
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* Permutations of numbers in an array using recursion
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* <br>
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* int numbers[] = {7,5,3};
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* LinkedList<LinkedList<Integer>> result = getAllPermutations(numbers);
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*/
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public static final LinkedList<LinkedList<Integer>> getAllPermutations(final int[] numbers){
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final LinkedList<LinkedList<Integer>> result = new LinkedList<LinkedList<Integer>>();
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return getAllPermutations(numbers, result);
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}
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private static final LinkedList<LinkedList<Integer>> getAllPermutations(final int[] numbers, LinkedList<LinkedList<Integer>> result){
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//numbers given in an array are also a permutation
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LinkedList<Integer> firstPermutation = new LinkedList<Integer>();
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for(int el : numbers){
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firstPermutation.add(new Integer(el));
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}
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result.add(firstPermutation);
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//let's permute all elements in array starting from index 0
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return permute(numbers, 0, result);
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}
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private static final LinkedList<LinkedList<Integer>> permute(final int[] numbers, int currentElementIndex, LinkedList<LinkedList<Integer>> result){
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if(currentElementIndex == numbers.length - 1)
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return result;
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for(int i = currentElementIndex; i < numbers.length; ++i){
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//swapping two elements
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int temp = numbers[i];
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numbers[i] = numbers[currentElementIndex];
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numbers[currentElementIndex] = temp;
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permute(numbers, currentElementIndex + 1,result);
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//all next permutation found
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if(i != currentElementIndex){
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LinkedList<Integer> nextPermutation = new LinkedList<Integer>();
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for(int j = 0; j < numbers.length; j++)
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nextPermutation.add(new Integer(numbers[j]));
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result.add(nextPermutation);
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}
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//swapping back two elements
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temp = numbers[i];
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numbers[i] = numbers[currentElementIndex];
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numbers[currentElementIndex] = temp;
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}
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return result;
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}
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}

‎src/com/jwetherell/algorithms/strings/StringFunctions.java

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@@ -242,45 +242,6 @@ public static final String[] generateSubsets(String inputString) {
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return output;
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}
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private static final int numberOfPermutations(int N) {
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// factorial
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int result = N;
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while (N > 1)
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result *= --N;
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return result;
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}
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private static final int permutations(String[] list, int index, char[] prefix, char[] remaining, int prefixLength, int remainingLength) {
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final int N = remainingLength-prefixLength;
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if (N == 0) {
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list[index]=new String(prefix);
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index++;
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} else {
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for (int i=0; i<N; i++) {
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final char[] prefChars = new char[prefixLength+1];
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System.arraycopy(prefix, 0, prefChars, 0, prefixLength);
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System.arraycopy(remaining, i, prefChars, prefixLength, 1);
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final char[] restChars = new char[N-1];
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System.arraycopy(remaining, 0, restChars, 0, i);
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System.arraycopy(remaining, i+1, restChars, i, N-(i+1));
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index = permutations(list, index, prefChars, restChars, remainingLength-(N-1), remainingLength);
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}
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}
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return index;
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}
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/** N! permutation of the characters of the string (in order) **/
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public static String[] permutations(String stringToGeneratePermutationsFrom) {
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final int size = numberOfPermutations(stringToGeneratePermutationsFrom.length());
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final String[] list = new String[size];
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final char[] prefix = new char[0];
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final char[] chars = stringToGeneratePermutationsFrom.toCharArray();
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permutations(list, 0, prefix, chars, 0, chars.length);
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return list;
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}
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/** recursive **/
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public static final int levenshteinDistanceRecursive(String s, String t) {
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final int sLength = s.length();

‎test/com/jwetherell/algorithms/mathematics/test/PermutationsTest.java

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package com.jwetherell.algorithms.mathematics.test;
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import static org.junit.Assert.assertEquals;
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import java.util.LinkedList;
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import org.junit.Assert;
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import org.junit.Test;
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import com.jwetherell.algorithms.mathematics.Permutations;
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public class PermutationsTest {
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@Test
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public void test1NumberOfPermutations() {
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int numbers[] = {1,2,3,4};
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int expectedNumberOfPermutations = 24;
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assertEquals(expectedNumberOfPermutations, (Permutations.getAllPermutations(numbers)).size());
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}
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@Test
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public void test2NumberOfPermutations() {
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int numbers[] = {3,4,2};
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int expectedNumberOfPermutations = 6;
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assertEquals(expectedNumberOfPermutations, (Permutations.getAllPermutations(numbers)).size());
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}
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@Test
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public void test3NumberOfPermutations() {
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int numbers[] = {3,4,2,5,4,9};
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int expectedNumberOfPermutations = 720;
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assertEquals(expectedNumberOfPermutations, (Permutations.getAllPermutations(numbers)).size());
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}
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@Test
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public void testComparePermutations() {
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int numbers[] = {4,2};
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LinkedList<Integer> firstPermutation = new LinkedList<Integer>();
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firstPermutation.add(4);
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firstPermutation.add(2);
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LinkedList<Integer> secondPermutation = new LinkedList<Integer>();
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secondPermutation.add(2);
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secondPermutation.add(4);
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LinkedList<LinkedList<Integer>> allPermutations = new LinkedList<LinkedList<Integer>>();
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allPermutations.add(firstPermutation);
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allPermutations.add(secondPermutation);
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assertEquals(allPermutations, Permutations.getAllPermutations(numbers));
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}
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@Test
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public void testPermutation1() {
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final String string = "abc";
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final String[] list = Permutations.permutations(string);
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Assert.assertTrue(list[0].equals("abc"));
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Assert.assertTrue(list[5].equals("cba"));
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}
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@Test
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public void testPermutation2() {
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final String string = "abcd";
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final String[] list = Permutations.permutations(string);
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Assert.assertTrue(list[0].equals("abcd"));
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Assert.assertTrue(list[5].equals("adcb"));
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Assert.assertTrue(list[11].equals("bdca"));
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Assert.assertTrue(list[17].equals("cdba"));
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Assert.assertTrue(list[23].equals("dcba"));
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}
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}

‎test/com/jwetherell/algorithms/strings/test/Strings.java

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import java.util.Arrays;
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import org.junit.Assert;
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import org.junit.Test;
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import com.jwetherell.algorithms.strings.StringFunctions;
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assertTrue("Edit Distance error. expected="+check+" got="+result, (check==result));
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}
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@Test
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public void testPermutation1() {
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final String string = "abc";
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final String[] list = StringFunctions.permutations(string);
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Assert.assertTrue(list[0].equals("abc"));
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Assert.assertTrue(list[5].equals("cba"));
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}
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@Test
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public void testPermutation2() {
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final String string = "abcd";
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final String[] list = StringFunctions.permutations(string);
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Assert.assertTrue(list[0].equals("abcd"));
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Assert.assertTrue(list[5].equals("adcb"));
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Assert.assertTrue(list[11].equals("bdca"));
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Assert.assertTrue(list[17].equals("cdba"));
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Assert.assertTrue(list[23].equals("dcba"));
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}
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private static final String print(String[] strings) {
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StringBuilder builder = new StringBuilder();
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for (String s : strings)

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