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Formula.java

 /* Copyright (c) 2010 the authors listed at the following URL, and/or
 the authors of referenced articles or incorporated external code:
 http://en.literateprograms.org/Quine-McCluskey_algorithm_(Java)?action=history&offset=20090311182700
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
 "Software"), to deal in the Software without restriction, including
 without limitation the rights to use, copy, modify, merge, publish,
 distribute, sublicense, and/or sell copies of the Software, and to
 permit persons to whom the Software is furnished to do so, subject to
 the following conditions:
 
 The above copyright notice and this permission notice shall be
 included in all copies or substantial portions of the Software.
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 Retrieved from: http://en.literateprograms.org/Quine-McCluskey_algorithm_(Java)?oldid=16251
 */
 
 import java.util.*;

 import java.io.*;

 
 
 class Formula {
     public Formula(List<Term> termList) {
         this.termList = termList;
     }
 
     public String toString() {
         String result = "";
         result += termList.size() + " terms, " + termList.get(0).getNumVars() + " variables\n";
         for(int i=0; i<termList.size(); i++) {
             result += termList.get(i) + "\n";
         }
         return result;
     }
 
     @SuppressWarnings("unchecked")
     public void reduceToPrimeImplicants() {
         originalTermList = new ArrayList<Term>(termList);
         int numVars = termList.get(0).getNumVars();
 	ArrayList<Term>[][] table = new ArrayList[numVars + 1][numVars + 1];
 	for(int dontKnows=0; dontKnows <= numVars; dontKnows++) {
 	    for(int ones=0; ones <= numVars; ones++) {
 	        table[dontKnows][ones] = new ArrayList<Term>();
 	    }
 	}
 	for(int i=0; i<termList.size(); i++) {
 	    int dontCares = termList.get(i).countValues(Term.DontCare);
 	    int ones      = termList.get(i).countValues((byte)1);
 	    table[dontCares][ones].add(termList.get(i));
 	}
 
         for(int dontKnows=0; dontKnows <= numVars - 1; dontKnows++) {
 	    for(int ones=0; ones <= numVars - 1; ones++) {
 	        ArrayList<Term> left   = table[dontKnows][ones];
 	        ArrayList<Term> right  = table[dontKnows][ones + 1];
 	        ArrayList<Term> out    = table[dontKnows+1][ones];
 	        for(int leftIdx = 0; leftIdx < left.size(); leftIdx++) {
 	            for(int rightIdx = 0; rightIdx < right.size(); rightIdx++) {
 	                Term combined = left.get(leftIdx).combine(right.get(rightIdx));
 	                if (combined != null) {
 	                    if (!out.contains(combined)) {
 	                        out.add(combined); 
 	                    }
 	                    termList.remove(left.get(leftIdx));
 			    termList.remove(right.get(rightIdx));
 			    if (!termList.contains(combined)) {
 			        termList.add(combined);
 			    }
 
 	                }
 	            }
 	        }
 	    }
 	}
 
     }
 
     public void reducePrimeImplicantsToSubset() {
         int numPrimeImplicants = termList.size();
 	int numOriginalTerms   = originalTermList.size();
 	boolean[][] table = new boolean[numPrimeImplicants][numOriginalTerms];
 	for (int impl=0; impl < numPrimeImplicants; impl++) {
 	    for (int term=0; term < numOriginalTerms; term++) {
 	        table[impl][term] = termList.get(impl).implies(originalTermList.get(term));
 	    }
 	}
 
         ArrayList<Term> newTermList = new ArrayList<Term>();
 	boolean done = false;
 	int impl;
 	while (!done) {
 	    impl = extractEssentialImplicant(table);
 	    if (impl != -1) {
 	        newTermList.add(termList.get(impl));
 	    } else {
 	        impl = extractLargestImplicant(table);
 	        if (impl != -1) {
 	            newTermList.add(termList.get(impl));
 	        } else {
 	            done = true;
 	        }
 	    }
 	}
 	termList = newTermList;
 
         originalTermList = null;
     }
 
     public static Formula read(Reader reader) throws IOException {
         ArrayList<Term> terms = new ArrayList<Term>();
         Term term;
         while ((term = Term.read(reader)) != null) {
             terms.add(term);
         }
         return new Formula(terms);
     }
 
 
     private int extractEssentialImplicant(boolean[][] table) {
         for (int term=0; term < table[0].length; term++) {
             int lastImplFound = -1;
             for (int impl=0; impl < table.length; impl++) {
                 if (table[impl][term]) {
                     if (lastImplFound == -1) {
                         lastImplFound = impl;
                     } else {
                         // This term has multiple implications

                         lastImplFound = -1;
                         break;
                     }
                 }
             }
             if (lastImplFound != -1) {
                 extractImplicant(table, lastImplFound);
                 return lastImplFound;
             }
         }
         return -1;
     }
 
     private void extractImplicant(boolean[][] table, int impl) {
         for (int term=0; term < table[0].length; term++) {
             if (table[impl][term]) {
                 for (int impl2=0; impl2 < table.length; impl2++) {
                     table[impl2][term] = false;
                 }
             }
         }
     }
 
     private int extractLargestImplicant(boolean[][] table) {
         int maxNumTerms = 0;
         int maxNumTermsImpl = -1;
         for (int impl=0; impl < table.length; impl++) {
             int numTerms = 0;
             for (int term=0; term < table[0].length; term++) {
                 if (table[impl][term]) {
                     numTerms++;
                 }
             }
             if (numTerms > maxNumTerms) {
                 maxNumTerms = numTerms;
                 maxNumTermsImpl = impl;
             }
         }
         if (maxNumTermsImpl != -1) {
             extractImplicant(table, maxNumTermsImpl);
             return maxNumTermsImpl;
         }
         return -1;
     }
 
 
     private List<Term> termList;
     private List<Term> originalTermList;
 
 
     public static void main(String[] args) throws IOException {
         Formula f = Formula.read(new BufferedReader(new FileReader(args[0])));
         f.reduceToPrimeImplicants();
         System.out.println(f);
         f.reducePrimeImplicantsToSubset();
         System.out.println(f);
     }
 
 }
 

Term.java

 /* Copyright (c) 2010 the authors listed at the following URL, and/or
 the authors of referenced articles or incorporated external code:
 http://en.literateprograms.org/Quine-McCluskey_algorithm_(Java)?action=history&offset=20090311182700
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
 "Software"), to deal in the Software without restriction, including
 without limitation the rights to use, copy, modify, merge, publish,
 distribute, sublicense, and/or sell copies of the Software, and to
 permit persons to whom the Software is furnished to do so, subject to
 the following conditions:
 
 The above copyright notice and this permission notice shall be
 included in all copies or substantial portions of the Software.
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 Retrieved from: http://en.literateprograms.org/Quine-McCluskey_algorithm_(Java)?oldid=16251
 */
 
 import java.util.*;

 import java.io.*;

 
 
 class Term {
     public static final byte DontCare = 2;
 
     public Term(byte[] varVals) {
         this.varVals = varVals;
     }
 
     public int getNumVars() {
         return varVals.length;
     }
 
     public String toString() {
         String result = "{";
         for(int i=0; i<varVals.length; i++) {
             if (varVals[i] == DontCare)
                 result += "X";
             else
                 result += varVals[i];
             result += " ";
         }
         result += "}";
         return result;
     }
 
     public Term combine(Term term) {
         int diffVarNum = -1; // The position where they differ

         for(int i=0; i<varVals.length; i++) {
             if (this.varVals[i] != term.varVals[i]) {
                 if (diffVarNum == -1) {
                     diffVarNum = i;
                 } else {
                     // They're different in at least two places

                     return null;
                 }
             }
         }
         if (diffVarNum == -1) {
             // They're identical

             return null;
         }
         byte[] resultVars = varVals.clone();
         resultVars[diffVarNum] = DontCare;
         return new Term(resultVars);
     }
 
     public int countValues(byte value) {
         int result = 0;
         for(int i=0; i<varVals.length; i++) {
             if (varVals[i] == value) {
                 result++;
             }
         }
         return result;
     }
 
     public boolean equals(Object o) {
         if (o == this) {
             return true;
         } else if (o == null || !getClass().equals(o.getClass())) {
             return false;
         } else {
             Term rhs = (Term)o;
             return Arrays.equals(this.varVals, rhs.varVals);
         }
     }
 
     public int hashCode() {
         return varVals.hashCode();
     }
 
     boolean implies(Term term) {
         for(int i=0; i<varVals.length; i++) {
             if (this.varVals[i] != DontCare &&
                 this.varVals[i] != term.varVals[i]) {
                 return false;
             }
         }
         return true;
     }
 
     public static Term read(Reader reader) throws IOException {
         int c = '\0';
         ArrayList<Byte> t = new ArrayList<Byte>();
         while (c != '\n' && c != -1) {
             c = reader.read();
             if (c == '0') {
                 t.add((byte)0);
             } else if (c == '1') {
                 t.add((byte)1);
             }
         }
         if (t.size() > 0) {
             byte[] resultBytes = new byte[t.size()];
             for(int i=0; i<t.size(); i++) {
                 resultBytes[i] = (byte)t.get(i);
             }
             return new Term(resultBytes);
         } else {
             return null;
         }
     }
 
 
     private byte[] varVals;
 }
 

input_example.txt

 000
 010
 011
 110
 101
 111
 

vastianos_example_1.3.txt

 0000
 0001
 0010
 0011
 0101
 0111
 1000
 1010
 1100
 1101
 1111