Loop 3.5 questions

Question

Note: they use xrange in the book we will use range

1. Translate the following for loops to equivalent while loops.
2. a.  for count in range(100):

            print count

       b. for count in range(1, 101):

            print count

       c. for count in range(100, 0, -1):

            print count

1. The factorial of an integer N is the product of all of the integers between 1

    and N, inclusive. Write a while loop that computes the factorial of a

   given integer N.

1. The log₂ of a given number N is given by M in the equation N = 2M.

   The value of M is approximately equal to the number of times N can

   be evenly divided by 2 until it becomes 0. Write a loop that computes

   this approximation of the log₂ of a given number N.

1. Describe the purpose of the break statement and the type of problem

    for which it is well suited.

1. What is the maximum number of guesses necessary to guess correctly a

    given number between the numbers N and M?

1. What happens when the programmer forgets to update the loop control

    variable in a while loop?

v

Answer 1

#0 - 99

for count in range(100):

print (count)

iStart = 0

iStop = 99

count = iStart

while (int(count)<=int(iStop)):

print (count)

count = count+1

#--------------------------------------

#1- 100

for count in range(1,101):

print (count)

iStart = 1

iStop = 100

count = iStart

while (int(count)<=int(iStop)):

print (count)

count = count+1

#-------------------------------------

#100 , 99, 98, ..., 3, 2, 1

for count in range(100, 0, -1):

print (count)

iStart = 100

iStop = 1

count = iStart

while (int(count)>=int(iStop)):

print (count)

count = count-1

#----------- Factorial -----------------

def Factorial( n):

factorialReturn=1

iCount = n

while (iCount>1):

factorialReturn = int(factorialReturn)*int(iCount)

iCount = int(iCount)-1

return factorialReturn

#---------------------------

for iLoop in range(26):

nBang = Factorial(iLoop)

print(str(iLoop) + "! = " + str(nBang))

#--------- Log ---------------------

def IntegralLogBase2( n ):

X = n

iCount=-1

while (int(X)!=0):

X = int(X)//2

iCount = int(iCount)+1

return iCount

#-------------

for i in range(1,101):

log2 = IntegralLogBase2(i)

print(" integral log of " + str(i) + " base 2 is " + str(log2))

#--------- Binary Search ---------------------------------------------

def BinarySearch(intArrayA, intTargetInt):

iIndexPos = -1

n=len(intArrayA)

Left=0

Right=int(n)-1

if ( int(intArrayA[0])==int(intTargetInt)):

iIndexPos=0

elif (int(intArrayA[n-1])==int(intTargetInt)):

iIndexPos=n-1

else:

while abs(int(Left) -int(Right))>1:

mid = (int(Left) + int(Right))//2

print("left = " + str(Left) + ": Right = " + str(Right) + ": Mid = " + str(mid))

if int(intArrayA[mid]) < int(intTargetInt):

Left = int(mid)

elif int(intArrayA[mid]) > int(intTargetInt):

Right = int(mid)

else: #found it!!!!

iIndexPos = mid

break

return iIndexPos

#------------------------------------

A = []

for iLoop in range(1,101):

A.append(iLoop)

intTargetInt=13

indexReturn = BinarySearch(A,intTargetInt)

if (indexReturn>-1):

print("Target integer " + str(intTargetInt) +" found at index position " + str(indexReturn) + ". \n Here it is :>" + str(A[indexReturn]) + "<")

else:

print("Sorry, Target integer " + str(intTargetInt) + " not found")

#------------------------------------------------------

"""

(1) break statement exists out of the INNER most loop

(2) Infinite loop occurs when you forget to update the

loop counter

(3) This is the binary search algorithmn which is order O(log N)

so Log_2(M-N)

"""