Binary operations #1

https://www.codewars.com/kata/binary-operations-number-1/train/csharp

Your work is to write a method that takes a value and an index, and returns the value with the bit at given index flipped.

The bits are numbered from the least significant bit (index 1).

Example:

FlipBit(15,4) == 7 // 15 in binary is 1111, after flipping 4th bit, it becomes 0111, i.e. 7
FlipBit(15,5) == 31 // 15 in binary is 1111, 5th bit is 0, after flipping, it becomes 11111, i.e., 31

using System;
public class Flip
{
    public static int FlipBit(int value, int bitIndex)
    {
        string str = Convert.ToString(value, 2).PadLeft(32,'0');
        var array = str.ToCharArray();
        int index = 32 - bitIndex;
        if (array[index] == '0')
        {
            array[index] = '1';
        }
        else
        {
            array[index] = '0';
        }
        str = string.Join(string.Empty,array);
        return Convert.ToInt32(str,2);
    }
}

对于给定的value，反转index位置上对应的bit。index从最右边开始为第一位。

using System;
public class Flip
{
    public static int FlipBit(int value, int bitIndex)
    {
        int Mask = 1 << (bitIndex - 1);
        return value ^ Mask;
    }
}