JZ15 二进制中1的个数

编程打卡第三天：

解法1：分情况讨论，用bin()

    def NumberOf1(self , n: int) -> int:
        # write code here
        result = 0
        result_neg = 0
        if n >= 0:
            binary_n = bin(n)
            for strs in str(binary_n):
                if strs == '1':
                    result += 1
            return result
        if n < 0:
            binary_n_neg = bin(abs(n))[2:]
            for strs in str(binary_n_neg):
                if strs == "0":
                    result_neg += 1
            result = 32- result_neg
            return result

解法2： 反码：n & 0xffffffff

    def NumberOf1(self , n: int) -> int:
        # write code here
        # -*- coding:utf-8 -*-
        # write code here
        if n < 0:
            n = n & 0xffffffff
        binNum = bin(n)[2:]
        arr = str(binNum)
        res = 0
        for ch in arr:
            if int(ch) == 1:
                res += 1
        return res