Reversing and adding numbers You will write a Python program

Reversing and adding numbers. You will write a Python program to implement the following procedure to produce palindromic numbers.

a) Take any positive integer x. If x is a palindrome, stop. Otherwise, continue to step (b).

b) Reverse the digits of x.

c) Add the reverse to x.

d) If the sum is a palindrome, then stop. Otherwise, let x represent the sum, and repeat steps (b) through (d).

Steps (b) through (d) represent a single iteration.

This is the code you should work on: Please try to explain using comments:

def reverse_add(low, high):
\'\'\' Executes the reverse and add algorithm for integers
in the range low to high. For example, if low is 10 and
high is 50, then the function would run the reverse and add
procedure on the numbers 10, 11, .., 49, 50. Or, the user could be interested in a single number such as 89. In
this case, low and high are both 89.
\'\'\'
  
# Write the rest of your code here.
print(\'low:\', low)
print(\'high:\', high)
  
  
def main():
\'\'\' The program driver. \'\'\'

# set cmd to anything except quit()
cmd = \'\'
  
# process the user commands
cmd = input(\'> \')
while cmd != \'quit\':
i = 0
while i < len(cmd) and cmd[i] != \' \':
i += 1
if \' \' in cmd:
low = int(cmd[:i+1])
high = int(cmd[i+1:])   
else:
low = int(cmd)
high = low
reverse_add(low, high)
cmd = input(\'> \')

main()

Solution

Please find the required program along with its output. Please see the comments against each line to understand the step.

def reverse(num): #function to reverse a int number
rev = 0   
while num > 0:
rev = (10*rev) + num%10
num //= 10
return rev

def reverse_add(low, high):
\'\'\' Executes the reverse and add algorithm for integers
in the range low to high. For example, if low is 10 and
high is 50, then the function would run the reverse and add
procedure on the numbers 10, 11, .., 49, 50. Or, the user could be interested in a single number such as 89. In
this case, low and high are both 89.
\'\'\'
  
# Write the rest of your code here.
print(\'low:\', low)
print(\'high:\', high)
  
if(low != high): #if low and high are not same numbers, means given is a range
for num in range(low,high+1): #iterate through the given range
steps = 0; #itialize steps
n = num
for i in range(0,100): #iterate the reverse and add method 100 times if reversly added digit is not palindrome
rev = reverse(n) #get the reverse of the number
if(n==rev): # if the number n and reverse rev are equal, means they are palindrom
stp = \' step\'   
if steps > 1 :
stp = \' steps\' #add steps if step is > 1
  
print num,\": PAL (\",steps,stp,\")\" #print output
break
n = n + rev # add reverse to the number n if n is not palindrome
steps = steps+1 #increment steps
if(n!=rev): #if n is not a palindrom
print num,\": NOT-PAL\"
  
elif(low == high): #if high and low are both same number, means user entered a single number, means not a range

steps = 0;
n = low
for i in range(0,100): #iterate the reverse and add method 100 times if reversly added digit is not palindrome
rev = reverse(n) #get the reverse
print steps,\". \",n,\" + \",rev,\" = \", (n+rev) #print each step
if(n==rev):
stp = \' step\'
if steps > 1 :
stp = \' steps\'
  
print low,\": PAL (\",steps,stp,\")\" #print output
break
n = n + rev
steps = steps+1
if(n!=rev):
print num,\": NOT-PAL\"
  
  
def main():
\'\'\' The program driver. \'\'\'
# set cmd to anything except quit()
cmd = \'\'
  
# process the user commands
cmd = raw_input(\'> \')
while cmd != \'quit\':
i = 0
while i < len(cmd) and cmd[i] != \' \':
i += 1
if \' \' in cmd:
low = int(cmd[:i+1])
high = int(cmd[i+1:])   
else:
low = int(cmd)
high = low
reverse_add(low, high)
cmd = raw_input(\'> \')
main()

-----------------------------------------------------

OUTPUT:

> 10 15
(\'low:\', 10)   
(\'high:\', 15)
10 : PAL ( 1 step )   
11 : PAL ( 0 step )   
12 : PAL ( 1 step )   
13 : PAL ( 1 step )   
14 : PAL ( 1 step )   
15 : PAL ( 1 step )   
> 84 91
(\'low:\', 84)   
(\'high:\', 91)
84 : PAL ( 2 steps )
85 : PAL ( 2 steps )
86 : PAL ( 3 steps )
87 : PAL ( 4 steps )
88 : PAL ( 0 step )   
89 : PAL ( 24 steps )   
90 : PAL ( 1 step )
91 : PAL ( 2 steps )
> 190 190
(\'low:\', 190)
(\'high:\', 190)   
0 . 190 + 91 = 281
1 . 281 + 182 = 463   
2 . 463 + 364 = 827   
3 . 827 + 728 = 1555
4 . 1555 + 5551 = 7106
5 . 7106 + 6017 = 13123   
6 . 13123 + 32131 = 45254   
7 . 45254 + 45254 = 90508   
190 : PAL ( 7 steps )   
> quit