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Java example source code file (TestGraphHuffman.java)

This example Java source code file (TestGraphHuffman.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

graphhuffman, hashset, string, testgraphhuffman, util

The TestGraphHuffman.java Java example source code

package org.deeplearning4j.graph.models.deepwalk;

import org.junit.Test;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotEquals;

public class TestGraphHuffman {

    @Test
    public void testGraphHuffman(){
        //Simple test case from Weiss - Data Structires and Algorithm Analysis in Java 3ed pg436
        //Huffman code is non-unique, but length of code for each node is same for all Huffman codes

        GraphHuffman gh = new GraphHuffman(7);

        int[] vertexDegrees = {10, 15, 12, 3, 4, 13, 1};

        gh.buildTree(vertexDegrees);

        for( int i=0; i<7; i++ ) System.out.println(i + "\t" + gh.getCodeLength(i) + "\t" + gh.getCodeString(i)
            + "\t\t" + gh.getCode(i) + "\t\t" + Arrays.toString(gh.getPathInnerNodes(i)));

        int[] expectedLengths = {3,2,2,5,4,2,5};
        for( int i=0; i<vertexDegrees.length; i++ ){
            assertEquals(expectedLengths[i], gh.getCodeLength(i));
        }

        //Check that codes are actually unique:
        Set<String> codeSet = new HashSet<>();
        for( int i=0; i<7; i++ ){
            String code = gh.getCodeString(i);
            assertFalse(codeSet.contains(code));
            codeSet.add(code);
        }

        //Furthermore, Huffman code is a prefix code: i.e., no code word is a prefix of any other code word
        //Check all pairs of codes to ensure this holds
        for( int i=0; i<7; i++ ){
            String code = gh.getCodeString(i);
            for( int j=i+1; j<7; j++ ){
                String codeOther = gh.getCodeString(j);

                if(code.length() == codeOther.length() ){
                    assertNotEquals(code,codeOther);
                } else if(code.length() < codeOther.length() ){
                    assertNotEquals(code,codeOther.substring(0,code.length()));
                } else {
                    assertNotEquals(codeOther,code.substring(0,codeOther.length()));
                }
            }
        }
    }
}

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