Reverse bits of a positive integer number in Python
Given an positive integer and size of bits, reverse all bits of it and return the number with reversed bits.Examples:
Input : n = 1, bitSize=32 Output : 2147483648 On a machine with size of bit as 32. Reverse of 0....001 is 100....0. Input : n = 2147483648, bitSize=32 Output : 1
We can solve this problem quickly in Python. Approach is very simple,
- Convert integer number into it’s binary representation using bin(num) function.
- bin() function appends 0b as a prefix in binary representation of number, skip first two characters of binary representation and reverse remaining part of string.
- As we know in memory any binary representation of a number is filled with leading zeros after last set bit from left that means we need to append bitSize – len(reversedBits) number of zeros after reversing remaining string.
- Now convert binary representation into integer number using int(string,base) method.
How int() method works ?
int(string,base) method takes a string and base to identify that string is referring to what number system ( binary=2, hexadecimal=16, octal=8 etc. ) and converts string into decimal number system accordingly. For example ; int(‘1010’,2) = 10.
Another way to revert bits without converting to string:
This is based on the concept that if the number (say N) is reversed for X bit then the reversed number will have the value same as:
the maximum possible number of X bits – N
= 2X – 1 – N
Follow the steps to implement this idea:
- Find the highest number that can be formed by the given number.
- Subtract the given number from that.
- Return the numbers.
Below is the implementation of the given approach.
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