Reverse bits in a number

[Pushpa]

Hii..
Can anyone pls post the program to reverse the bits of a number.

thank you in advance...

[WingedPanther]

No, but we can help you fix your code. Also, are you reversing bits or digits? Integer, float, other?

[Ewe Loon]

I would assume it would be for integers, as floating point numbers would get really messed up

you would want something like this

	int reverse(int n)
	{
		int r=0;
		int c;
		for (c=0;c<32;c++)
		{
			r=(r<<1)+(n & 1);
			n=n>>1;
		}
		return r;
	}

[MeTh0Dz]

I would assume it would be for integers, as floating point numbers would get really messed up

you would want something like this

	int reverse(int n)
	{
		int r=0;
		int c;
		for (c=0;c<32;c++)
		{
			r=(r<<1)+(n & 1);
			n=n>>1;
		}
		return r;
	}

This code is bad for a number of reasons.

1) You assume that integers are 32 bits.

2) Hence I bet you are assuming that integers are 4 bytes and that a byte is always 8 bits. This is wrong.

3) You should use C99 styled for loops.

4) In general this is a bad implementation.

[dargueta]

This better?

#include <limits.h>

/*
if you're using C++ do
# include <climits>
*/

#define     INT_BITS        sizeof(int) * CHAR_BITS

int reverse(int input)
{
    int hbit;
    int mask = 1 << (INT_BITS - 1);     /* 0x80000000 for 32-bit ints */
    
    for(unsigned int i = 0; i < INT_BITS; ++i)
    {
        hbit = input & mask;
        input <<= 1;
        input |= hbit;
    }
    
    return input;
}

[Ewe Loon]

well next time i wont bother

[dargueta]

Why?