****************Q1P1********************************
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/*Write a program to compute the total amount due, including sales tax.

Ask the user how many of each item are needed:
Pencils are fifteen cents ($0.15) each.
Paper is once cent ($0.01) per sheet.
An eraser costs fifty cents ($0.50).
The sales tax rate is  of 8.625% (0.08625).

Extra credit for rounding off the total to the nearest cent ($0.01).*/


////  PURPOSE:  Calculate mean average of 5 numbers.
////  AUTHOR:   Zhilin Kuang

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
  	Scanner input = new Scanner (System.in);
  	double a, b, c, d, e, avr;
  	System.out.print ( "Enter your first number: ");
  	a = input.nextDouble ();
  	System.out.print ( "Enter your second number: ");
  	b = input.nextDouble ();
  	System.out.print ( "Enter your third number: ");
  	c = input.nextDouble ();
  	System.out.print ( "Enter your fourth number: ");
  	d = input.nextDouble ();
  	System.out.print ( "Enter your fifth number: ");
  	e = input.nextDouble ();
  	avr = (a+b+c+d+e)/5;
  	
  	System.out.println ( "The mean average of the five numbers you entered is: " + avr);

  }
}



****************Q1P2********************************
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/*q1b:  Write another java program (to do IPO):

Compute the volume of a cylinder, given its radius and height.
Input the radius and height.
Compute the volume.
Output the result

q1b: = exercise 2.2 on page 69.   Write a java program that computes the volume of a cylinder.
The formula for volume of a cylinder is:  
volume = area * height
The formula for the area of the circular base is
area = PI * Math.pow( radius, 2 )*/


//// QUIZ 1, PROBLEM 2 Compute the volume of a cylinder
//// Zhilin Kuang

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
  	Scanner input = new Scanner (System.in);
  	double area, height, radius, volume;
    System.out.print("Enter the radius and height of a cylinder: ");
    radius = input.nextDouble();
    height = input.nextDouble();
    area = 3.1415926 * Math.pow (radius, 2);
    volume = area * height;
    System.out.println ("The volume of the cylinder is: " 
    + volume);
  }
}



****************Q1P3********************************
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////  r1c:  REDO QUIZ #1 PROBLEM 3:  roots of a quadratic.
////  AUTHOR:   Zhilin Kuang

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
	Scanner input = new Scanner (System.in);
	double a, b, c, root, root2;
	
	// Input 
	System.out.print ( "For a function f(x)=ax^2+bx+c, please enter coefficient a:");
	a = input.nextDouble ();
	System.out.print ( "Enter coefficient b:");
	b = input.nextDouble ();
		System.out.print ("Enter coefficient c:");
	c = input.nextDouble ();
	
	// Process
	root = (-b + Math.sqrt (Math.pow(b,2)-4*(a*c)))/(2*a);
	root2 = (-b - Math.sqrt (Math.pow(b,2)-4*(a*c)))/(2*a);
	
	//Output
	System.out.print ( "The roots for this function are: " + root + " and " + root2);
  }
}



****************Quiz 2********************************
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//// REDO #2 (November 2016)
//// CST 112 [aft]:  Zhilin Kuang

import java.util.Scanner;
class Main {

  static String lastName, firstName, winner, pw;
  static int areaCode, zipCode, n5, count=0, countl, countf, fac, n1;
  static double answer1, answer2, answer3, answer4, answer5, sd;
  static Scanner r=  new Scanner( System.in );	


  //// MAIN PROGRAM ////
  public static void main(String[] args) {

	lastName=	"Kuang";	
	firstName=	"Zhilin";		


  	// Title //
    say( "\nCST 112 [aft] Quiz # 2:  " + lastName +" "+firstName );

    answer1=answer2=answer3=answer4=answer5=countl=countf=0;
    
    //  TASK 1. Count the number of consonants in each String (firstName and lastName),
	//  	then print a message saying which one (if any) has more of them.
	
	// count consonants in last name
	say("\nTask 1");
	for (int i = 0; i < lastName.length(); i++) {
      if (isConsonant(lastName.charAt(i)))
       countl++;
    }
    
    // count consonants in first name
    for (int i = 0; i < firstName.length(); i++) {
      if (isConsonant(firstName.charAt(i)))
       countf++;
    }
    
    // compare numbers of consonants
    if (countf>countl){
    	winner=firstName;
    }
    else {
    	winner=lastName;
    }
    
    // output result
    say ("There are " + countl + " consonants in your last name and " + countf+ " consonants in your first name.");
    say ( winner + " has more consonants.");
			
	//  TASK 2. Check whether area code has exactly three digits; print error message if not.
	//  	Check whether area code has exactly three digits; print error message if not.
	say("\nTask 2");
	while (countDigits (areaCode)!=3){
		areaCode=	ask( "What is your area code?  ");
		if (countDigits(areaCode)!=3) {
		say("Invalid area code! ");
		}
	}
	
	while (countDigits (zipCode)!=5){
		zipCode= ask( "What is your zip code?   ");
		if (countDigits (zipCode)!=5){
		say("Invalid zip code! ");
		}
	}
	 	
	//  TASK 3. Check to see if each number (zipCode and areaCode) is divisible by
    //  	any of the first six primes (2, 3, 5, 7, 11, 13).
    say("\nTask 3");
    for (int i=0; i<=13; i++) {
    	if (isPrime(i) && (isMult( zipCode, i)){
    		say ("Zip code is divisible by", i);
    	}
    }
    for (int i=0; i<=13; i++) {
    	if (isPrime(i) && (isMult( areaCode, i)){
    		say ("Area code is divisible by", i);
    	}
    }
    
	//  TASK 4. Calculate and print the factorials of the numbers one to twelve.
	say("\nTask 4");
    for (int i=1; i<=12; i++){
    	fac= factorial (i);
    	System.out.println("The factorial of "+i+ " is "+fac+ " ");
    }
		
	 //  TASK 5. Prompt the user to enter a password; check if it follows these rues:.
	 //  	-- between five and fifteen characters long.
	 //  	-- exactly three digit characters.
	 //  	-- more consonats than vowels.
     //  	-- at least one character that is not a letter or number.
     say("\nTask 5");
     // Prompt to enter password
     pw= askString ("Enter your password:");
     if (isValidPassword(pw)) {
      System.out.println("Valid password");
    }
    else {
      System.out.println("Invalid password");
    }

		// OPTIONAL:  Instead of writing code here (in main), 
		// OPTIONAL:  write a separate method for each of the above
		// OPTIONAL:  and call it with appropriate arguments.
	
	// Now, calculate the five answers, as described in the web page for Quiz #2. //
	// answer 1
	int answer1=0;
    while (Math.pow(answer1,2) <=zipCode){
      answer1++;	
    }
    
    // answer 2
    answer2 = sumFactorial(zipCode);
    
    // answer 3
    answer3 = Math.toDegrees(Math.acos(3.0/5.0));
    
    //answer 4
    answer4 = Math.sqrt(Math.pow(zipCode,2) + Math.pow(areaCode,2));

	// answer5
	say ("\n");
	do {
		n5=ask ( "Enter a non-zero number:" );
		answer5+= Math.pow(n5, 2);
		count++;
	} while (n5!=0);
	
	// Standard deviation
	sd= Math.sqrt(answer5/(count-1));
	
	// Show the answers
	say( "\nANSWERS:" );
	say( "Answer #1 is:  ", answer1 );
	say( "Answer #2 is:  ", answer2 );
	say( "Answer #3 is:  ", answer3 );
	say( "Answer #4 is:  ", answer4 );
	say( "Answer #5 is:  ", answer5 );
	say( "Standard deviation of the numbers entered is", sd );
	
  }// END of main()//
  
  //methods
  public static int factorial (int n){
  	int result=1;
  	if (n==0){
  		return result;
  	}
  	else {
  		for (int i=1; i<=n; i++){
  		result= result*i;
  	   }
  	
  	return result;
    }
  }
  
  public static int sumDigits( int n) {
    int result=0, remainder=0; 
  	for ( int i = n; i>0; i=i/10 )
    remainder += i % 10 ;
    result += remainder;
    return result;
    }

 public static boolean isMult( int number, int factor ) {
  	boolean result;
  	if (number % factor == 0) {
  		result=true;
  	}
  	else{
  		result=false;
  	}
  	return result;
  }

 public static boolean isVowel (char c){
 	if (Character.isLetter (c)) {
 		switch (Character.toLowerCase(c)) {
  	       case 'a': 
           case 'e': 
           case 'i': 
           case 'o': 
           case 'u': return true;
           default: return false;
       }
 	}
 }
 
 public static boolean isConsonant (char c){
 	if (Character.isLetter (c) && !isVowel (c)){
 		return true;
 	}
 	else {
 		return false;
 	}
 }
 
 public static int countDigits( int n) {
  	int count=0; 
  	for ( int i = n; i>0; i=i/10 )
  	count++;
  	return count;
  }
  
  public static boolean isValidPassword(String s) {
    // Check length
    if (s.length() < 5 && s.length() > 15 )
      return false;
    
     // at least one character that is not a letter or a digit
    for (int i = 0; i < s.length(); i++) {
      if (!Character.isLetter(s.charAt(i)) && 
          !Character.isDigit(s.charAt(i)))
        return true;
      else {
      	return false;
      }
        }
    
    // Count exactly three digit of characters
    int count = 0;
    for (int i = 0; i < s.length(); i++) {
      if (Character.isLetter(s.charAt(i)))
        count++;
    }
    if (count == 3)
      return true;
    else 
      return false;
      
    // check if more consonats than vowels
    /*for (int i = 0; i < s.length(); i++) {
      if (Character.isLetter(s.charAt(i)) && isConsonant(s.charAt(i))){
       count++;
      }
    }
    return false;*/
    }
    
    public static int sumFactorial( int n) {
    	int result=0, remainder, fact=0; 
  	    for ( int i = n; i>0; i=i/10 )
  	    fact += factorial(i % 10 );
  	    result += fact;
  	    return result;
    }
    
    public static boolean isPrime ( int a ) {
  	    boolean result;
  	    int f=a, n=0;
  	    while ( f>1) {
  			f--;
  			if (a%f == 0) {
  				n+=f;
  			} 
  		} 
  	    if (n>1||a==0) {
  		result=false;
      	}
    	else{
  		result=true;
    	}
    	return result;
  }
  
  //++++++ PLEASE DO NOT ADD ANY NEW CODE BELOW THIS LINE. ++++++++//

  //// I/O METHODS ////
  // Display a String (and/or a value) on a line.
  public static void say( String s ) 			{ System.out.println( s ); }
  public static void say( String s, double x )	{ System.out.println( s +":  "+ x ); }
  public static void say( double x ) 			{ System.out.println( x ); }
  
  // Display prompt (w/o NL); prompt and return input.
  public static void prompt( String s ) 		{ System.out.print( s ); 
  }
  public static int ask( String s ) 			{ prompt( s ); return r.nextInt(); }
  public static String askString( String s )	{ prompt( s ); return  r.next(); }

}//END OF class Main//




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