Compute how many bits to require convert one integer to another

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Problem

Write a function to determine the number of bits required to convert integer A to integer B.
Input: 31, 14
Output: 2

Solution

using System;

namespace JamesChen

{

class BitDifference

{

static int CalculateBitDifference(int a, int b)

{

int count = 0;

a = a ^ b;

while (a != 0)

{

a &= (a - 1);

count++;

}

return count;

}

static void DoTest(int a, int b)

{

Console.WriteLine("a = {0, 4}, b = {1, 4}", a, b);

Console.WriteLine("{0, 32} -- a", Convert.ToString(a, 2));

Console.WriteLine("{0, 32} -- b", Convert.ToString(b, 2));

Console.WriteLine("requires {0} bit convert a to b",

CalculateBitDifference(a, b));

Console.WriteLine("-----------------------------------");

}

static void Main(string[] args)

{

DoTest(31, 14);

DoTest(14, 31);

DoTest(-2, 0);

DoTest(0, -2);

DoTest(-5, -20);

DoTest(-20, -5);

}

Output

a = 31, b = 14

11111 -- a

1110 -- b

requires 2 bit convert a to b

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

a = 14, b = 31

1110 -- a

11111 -- b

requires 2 bit convert a to b

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

a = -2, b = 0

11111111111111111111111111111110 -- a

0 -- b

requires 31 bit convert a to b

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

a = 0, b = -2

0 -- a

11111111111111111111111111111110 -- b

requires 31 bit convert a to b

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

a = -5, b = -20

11111111111111111111111111111011 -- a

11111111111111111111111111101100 -- b

requires 4 bit convert a to b

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

a = -20, b = -5

11111111111111111111111111101100 -- a

11111111111111111111111111111011 -- b

requires 4 bit convert a to b

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

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