将一个4字节整数的二进制表示中的001替换为011

题目：将一个4字节整数的二进制表示中的001替换为011

答：

int replace(int num)
{
    unsigned int mode3bit = 7;
    unsigned int mode1bit = 1;
    int shift = 0;
    int result = 0;
    while (shift < 32)
    {
        while (shift < 32 && (num & (mode3bit<<shift)) != (1<<shift))
        {
            result += (num & (mode1bit<<shift));
            shift++;
        }
        if (shift >= 32)
        {
            break;
        }
        else if (32 - shift < 3)  //高位不足3位
        {
            result += (num & (mode3bit<<shift));
            break;
        }
        result += (3<<shift);
        shift += 3;
        
    }
    return result;
}

int _tmain(int argc, _TCHAR* argv[])
{
    int num = 12345678;                        //0b0000 0000 1011 1100 0110 0001 0100 1110
    assert(29156190 == replace(num)); //29156190 0b0000 0001 1011 1100 1110 0011 0101 1110

    num = 1227133513;                              //0b0100 1001 0010 0100 1001 0010 0100 1001
    assert(1533916891 == replace(num)); //1533916891 0b0101 1011 0110 1101 1011 0110 1101 1011

    num = 613566757;                               //0b0010 0100 1001 0010 0100 1001 0010 0101
    assert(1840700269 == replace(num)); //1840700269 0b0110 1101 1011 0110 1101 1011 0110 1101

    num = -809737911;                              //0b1100 1111 1011 1100 0110 0001 0100 1001
    assert(-541269157 == replace(num)); //-541269157 0b1101 1111 1011 1100 1110 0011 0101 1011

    num = -920350135;                                //0b1100 1001 0010 0100 1001 0010 0100 1001
    assert(-613566757 == replace(num)); //-613566757 //0b1101 1011 0110 1101 1011 0110 1101 1011

    return 0;
}