Abhijeet Pal: Python Program To Reverse a Number

Problem Definition Create a Python program to reverse a number in Python. Solution This article will show multiple solutions for reversing a number in Python. Reversing a number mathematically The algorithm below is used to reverse a number mathematically with time complexity of O(log n) where n is input number. Algorithm Input : num (1) Initialize rev_num = 0 (2) Loop while num > 0 (a) Multiply rev_num by 10 and add remainder of num divide by 10 to rev_num (b) Divide num by 10 (3) Return rev_num  Program num = 12345 rev_num = 0 while num != 0: rev_num = rev_num * 10 rev_num = rev_num + (num%10) num = num // 10 print(rev_num) Output 54321 Using reversed() method Python’s built in reversed() method returns an iterator that accesses the given sequence in the reverse order. Program # input num = 1234 rev_iterator = reversed(str(num)) rev_num = "".join(rev_iterator) print(rev_num) Output 4321 Note that the reversed() method doesn’t accept integer as a parameter therefore data type is converted to a string. Sincereversed() returns an iterator we need to join it …

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