Leetcode--两道简单的二进制问题

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).

For example, the 32-bit integer ’11' has binary representation 00000000000000000000000000001011, so the function should return 3.【对于一个32位无符号数整数返回它的的二进制表示形式中的1的个数】

Python解决方案：

class Solution:
    def hammingWeight(self, n):
        if n == 0:
            return 0
        i = 0
        while (n!=0 ):
            if n==1:
                return i+1
            if n%2 == 1:
                i=i+1
            n = (n-n%2)/2
        return i

Reverse Bits：

Reverse bits of a given 32 bits unsigned integer.

For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as00111001011110000010100101000000).【将一个32位无符号数的二进制表示形式（前面补0使其长度为32位）倒叙，然后转换为十进制】

Python解决方案：

class Solution:
    # @param n, an integer
    # @return an integer
    def reverseBits(self, n):
        if n==0:
            return 0
        str = "" #str存储着这个数的二进制形式的倒叙（没有补0时）
        while(n!=0):
            if n == 1:
                str +="1"
                break
            if(n%2==0):
                str +="0"
            else:
                str += "1" 
            n=(n-n%2)/2
        result = 0
        Flag = 32  #表示i在第几位
        for i in str:
            if i=="1":
                result +=pow(2,Flag-1)
            Flag = Flag-1
        return result