import java.util.*;

public class Assignment{

  boolean arrVals[];
    
  //POST:  creates an assignment which can hold the values for numVals boolean variables
public Assignment(int numVals){
  arrVals = new boolean[numVals];
  for(int i=0;i<numVals;i++){
    arrVals[i] = false;
  }
}

  //POST: res is the number of vars being stored
public int size(){ return arrVals.length;}

    //PRE: varNum is a legal variable number
    //POST: returns the truth assignment of the varNum'th variable
public boolean getVarVal(int varNum){
  return arrVals[varNum];
}

  //POST: RES is a random bit
public static boolean randomBit(Random r){
  int x = r.nextInt();
  int y = r.nextInt();
  return (x<y);
}

  //POST: randomizes the boolean values of this object.
public void randomize(){
  Random rand = new Random();
  //rand is a random number generator.

  for(int i=0;i<arrVals.length;i++){
    boolean randVal = randomBit(rand);
    arrVals[i] = randVal;
  }
}    

  //PRE: varNum is a legal variable number
  //POST: RES is a *new* Assignment object with the same values as this object except the varNum'th truth value is flipped.
public Assignment flipVarVal(int varNum){
  int size = arrVals.length;
  Assignment res = new Assignment(size);
  for(int i=0;i<size;i++){
    res.arrVals[i] = arrVals[i];
  }
  
  boolean currVal = arrVals[varNum];
  res.arrVals[varNum] = !currVal;
  return res;
}

  //PRE: dVar maps from strings(var names) to numbers.  All of the strings in dVar map to numbers which are valid ids in this.
  //POST: returns a string where each line gives a variable name in dVarfollowed by its truth value.
  String toString(Dictionary dVar){
    Enumeration enum = dVar.keys();
    String sRes = "";
  
    while(enum.hasMoreElements()){
      String sCurrVar = (String)enum.nextElement();
      Integer i = (Integer)dVar.get(sCurrVar);
      int id = i.intValue();
      boolean truthVal = getVarVal(id);
      
      String sTruthVal = "false";
      if(truthVal){
	sTruthVal = "true";
      }
      String sLine = sCurrVar + " " + sTruthVal + "\n";
      sRes = sRes + sLine;
    }
    return sRes;
  }
    

}