Input=12345 output=54321
Program to write a reverse of numbers
n=int(input("Enter number :"))
rev=0
while(n>0):
dig = n%10
rev=rev*10+dig
n=n//10
print("The reverse of the number:" ,rev)
Can some explain why this print 54321
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6 Answers
You can iterate a string in python, and you'll be iterating by each character
There you go:
a = input("Enter : ")
x = [num for num in a] # Getting the individual digits
b = reversed(x) # reversed() is a built in function
print("".join(b))
Comments
This is much simpler
inp = input("Enter the number")
list1 = [numbers for numbers in inp]
list2 = [reversed_numbers for reversed_numbers in list1[::-1]]
print("".join(list2))
Comments
This should work
number = int(input("Enter a number: "))
rev = ''
while number > 0:
last_digit = number % 10 #The remainder when it's divided by 10 will always be the last digit
rev = rev + str(last_digit)
number = number // 10
print("Reversed : ", rev)
Comments
Let, n = 12345 , where 12345 is the given input.
rev = 0
Now in the first iteration of the while loop n > 0
dig = remainder of n divided by 10, So it is = 5
rev = rev(0) * 10 + dig(5) = 5
n = n // 10 = 1234
In the second iteration n = 1234 which is > 0
rev = 5
dig = remainder of n divided by 10, So it is = 4
rev = rev(5) * 10 + dig(4) = 54
n = n // 10 = 123
In the third iteration n = 123 which is > 0
rev = 54
dig = remainder of n divided by 10, So it is = 3
rev = rev(54) * 10 + dig(3) = 543
n = n // 10 = 12
In the fourth iteration n = 12 which is > 0
rev = 543
dig = remainder of n divided by 10, So it is = 2
rev = rev(543) * 10 + dig(2) = 5432
n = n // 10 = 1
In the fifth iteration n = 1 which is > 0
rev = 5432
dig = remainder of n divided by 10, So it is = 1
rev = rev(5432) * 10 + dig(1) = 54321
n = n // 10 = 0
Now in the sixth iteration of the while loop n = 0 so it is not greater than 0 so loop will break and you got rev = 54321
Comments
It's actualy pretty simple
1st iteration
- Well you first get % of 10 which is basicaly last number (residual) dig = 5,
- than you add this to rev*10 (in first iteration 0) + dig = 5,
- and you whole nuber divide the n by 10 (deleting last nuber) n = 1234
2nd iteration
- dig = 4
- rev =5*10 + 4 = 54
- n = 123
3rd iteration
- dig = 3
- rev = 540 + 3 = 543
- n = 12
...
However there is much easier way how to do this eg.
If your input is string so you just need to reverse it
input = "12345"
output = input[::-1]
If input is number (int, float) than you have to convert it to string
input = 12345
output = str(input)[::-1]
And convert back
int(output)
Comments
See other answer for great explanations. Here I add 2 simpler solutions to the original problem - how to reverse a number:
# For example, 12345:
num = input("Enter number: ")
# fastest and shortest:
rev = num[::-1]
# or (slower and longer)
rev = "".join(reversed(num))
print(f"The reverse of the number: {rev}")
# The reverse of the number: 54321
