WMDD 4820 - Quiz 3

quiz3.js

// 1. How many times are the following loop bodies repeated?
// What is the printout of each loop? (3 points)

// a.
var i = 1;
while (i < 10)
  if (i % 2 == 0)
    document.write( i + "<br />");

// Answer: infinity loop. i will be never incremented.

// b.
var i = 1;
while (i < 10)
  if (i % 2 == 0)
    document.write( i++ + "<br />");

// Answer: infinity loop. i will be never incremented.

// c.
var i = 1;
while (i < 10)
  if (i++ % 2 == 0)
    document.write( i );

// Answer:
// 3
// 5
// 7
// 9

// -----------------------------------------------------------------------------

// 2. Will the following programs terminate? If so, give the output. (4 points)

// a.

var balance = 49;
while (true)
{
  if (balance < 9)
    break;
  balance = balance - 9;
}
document.write ( "Balance is " + balance );

// Answer: Balance is 4

// b.

var balance = 49;
while (true)
{
  if (balance < 9)
    continue;
  balance = balance - 9;
}
document.write ( "Balance is " + balance );


// -----------------------------------------------------------------------------

// 3. Show the output of the following code segments. (6 points)

// a.
var i = 0;
while (i < 4)
{
  for (var j = i; j > 1; j--)
    document.write ( j );
  document.write( "****" + "<br/>" );
  i++;
}

// Answer:
// ****
// ****
// 2****
// 32****

// b.

var i = 4;
while (i >= 1)
{
  var num = 1;
  for (var j = 1; j <= i; j++)
  {
    document.write( num + "xxx" );
    num *= 2;
  }
  document.write( "<br/>" );
  i--;
}

// Answer:
// 1xxx2xxx4xxx8xxx
// 1xxx2xxx4xxx
// 1xxx2xxx
// 1xxx

// c.
var row = 4;
while ( row >= 1 ) {
  column = 1;
  while ( column <= 5 ) {
    document.write ( row % 2 ? "<" : ">" );
    ++column;
  }
  --row;
  document.write("<br/>");
}

// Answer
// >>>>>
// <<<<<
// >>>>>
// <<<<<

// -----------------------------------------------------------------------------

// 4. How many times is the print statement executed? (2 points)

for (var i = 0; i < 10; i++)
  for (var j = 0; j < i; j++)
    document.write( i * j + "<br/>");

// Answer: 45 times