parser.java

Create a problem solver for linear programming

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package ro.utils;

import java.util.ArrayList;
import ro.simplex.*;

/**
 *
 * @author Doan Chien Thang
 */
public class Parser {
    protected ArrayList<Variable> vars = new ArrayList<Variable>();
    protected ArrayList<Fraction> objCoefs = new ArrayList<Fraction>();
    protected ArrayList<Constraint> constraints = new ArrayList<Constraint>();
    
    public boolean isExistVariable(int index) {
        for (int i = 0; i < vars.size(); i++)
            if (vars.get(i).getIndex() == index)
                return true;
        return false;
    }

    public Objective parseObjective(String objInput) {
        String elements[] = objInput.split("=");
        int type = elements[1].trim().compareTo("max") == 0 ?
            Objective.MAXIMIZE : Objective.MINIMIZE;
        String tmp = "";
        for (int i = 0; i < elements[0].length(); i++) {
            if (elements[0].charAt(i) == '+' || elements[0].charAt(i) == '-')
                tmp += "*";
            if (elements[0].charAt(i) != ' ')
                tmp += elements[0].charAt(i);
        }
        String prefix = "x";
        String varsStr[] = tmp.split("\\*");
        for (int i = 0; i < varsStr.length; i++) {
            Fraction coef;
            String s[] = varsStr[i].split("x");
            //System.out.println("__" + s[0]);
            if (s[0].charAt(0) == '+')
                coef = new Fraction(Integer.parseInt(s[0].substring(1)));
            else if (s[0].charAt(0) == '-') {
                coef = new Fraction(Integer.parseInt(s[0].substring(1)));
                coef = coef.getOpposite();
            } else
                coef = new Fraction(Integer.parseInt(s[0]));
            int index = Integer.parseInt(s[1]);
            Variable var = new Variable (null, index, "x", ConstraintTypes.GREATER_THAN);
            vars.add(var);
            objCoefs.add(coef);
        }
        return new Objective(type, objCoefs, vars, new Fraction(0));
    }

    public Constraint parseConstraint(String conStr) {
        ArrayList<Fraction> coefs = new ArrayList<Fraction>();
        String elements[];
        int type;

        if (conStr.indexOf(">") > -1) {
            elements = conStr.split(">=");
            type = ConstraintTypes.GREATER_THAN;
        }
        else if (conStr.indexOf("<") > -1) {
            elements = conStr.split("<=");
            type = ConstraintTypes.LESS_THAN;
        }
        else {
            elements = conStr.split("=");
            type = ConstraintTypes.EQUAL_TO;
        }
        //System.out.println(elements[1]);
        String val = elements[1].trim();
        Fraction value;
        if (val.charAt(0) == '-') {
            val = val.substring(1);
            value = new Fraction(Integer.parseInt(val));
            value = value.getOpposite();
        } else
            value = new Fraction(Integer.parseInt(val));
        String tmp = "";
        for (int i = 0; i < elements[0].length(); i++) {
            if (elements[0].charAt(i) == '+' || elements[0].charAt(i) == '-')
                tmp += "*";
            if (elements[0].charAt(i) != ' ')
                tmp += elements[0].charAt(i);
        }
        System.out.println(tmp);
        tmp = tmp.trim();
        if (tmp.charAt(0) == '*')
            tmp = tmp.substring(1);
        String varsStr[] = tmp.split("\\*");
        System.out.println();
        for (int i = 0; i < varsStr.length; i++)
            System.out.printf("+%20s+", varsStr[i]);
        System.out.println();
        for (int i = 0; i < varsStr.length; i++) {
            Fraction coef;
            String s[] = varsStr[i].split("x");
            System.out.println("__" + s[0]);
            if (s[0].charAt(0) == '+')
                coef = new Fraction(Integer.parseInt(s[0].substring(1)));
            else if (s[0].charAt(0) == '-') {
                coef = new Fraction(Integer.parseInt(s[0].substring(1)));
                coef = coef.getOpposite();
            } else
                coef = new Fraction(Integer.parseInt(s[0]));
//            int index = Integer.parseInt(s[1]);
            //Variable var = new Variable (null, index, "x", ConstraintTypes.GREATER_THAN);
            //vars.add(var);
            coefs.add(coef);
        }
        return new Constraint(type, coefs, vars, value);
    }

    public boolean isVariableConstraint(String input) {
        String s[] = input.split(" ");
        return (s.length == 3 && s[s.length - 1].compareTo("0") == 0);
    }

    public Problem parse(String objInput, String consInput) {
        Objective objective = this.parseObjective(objInput);
        ArrayList<Constraint> contraints = new ArrayList<Constraint>();
        String s[] = consInput.split("\\n");
        for (int i = 0; i < s.length; i++)
            System.out.println(s[i]);
        for (int i = 0; i < s.length; i++) {
            if (!isVariableConstraint(s[i]))
                constraints.add(parseConstraint(s[i]));
            else
                parseVariable(s[i]);
        }
        Problem p = new Problem(vars, constraints, objective);
        System.out.println(p);
        return p;
    }

    public void parseVariable(String varStr) {
        int constraint;
        if (varStr.indexOf(">") > -1)
            constraint = ConstraintTypes.GREATER_THAN;
        else if (varStr.indexOf("<") > -1)
            constraint = ConstraintTypes.LESS_THAN;
        else
            constraint = ConstraintTypes.BELONG_R;
        String elements[] = varStr.split(" ");
        int varIndex = Integer.parseInt(elements[0].substring(1).trim());
        for (int i = 0; i < vars.size(); i++)
            if (vars.get(i).getIndex() == varIndex)
                vars.get(i).setConstraint(constraint);
    }

    public static void main(String[] args) {
        Parser p = new Parser();
        Objective s = p.parseObjective("7x1 + 2x2 - 1x3 = max");
        //System.out.println(s.toString());
        Constraint constraint = p.parseConstraint("7x1 + 2x2 - 1x3 <= 122");
        String objInput = "3x1 + 5x2 = max";
        String consOutput = "0x1 + 2x2 <= 12\n" +
                "1x1 - 2x2 <= -2\n" + "-3x1 - 2x2 <= -18\n" + "x1 >= 0\nx2 >= 0";
        Problem problem = p.parse(objInput, consOutput);
        System.out.println(problem.toString());
    }
}