leetcode 371. Sum of Two Integers

Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.

Example:
Given a = 1 and b = 2, return 3.

只能位运算：

0x01101011 ^

0x00111001

----------

0x01010010

0x01101011 &

0x00111001

---------

0x00101001 <<1

---------

0x01010010

class Solution {
public:int getSum(int a, int b) {if (a==0) return b;return getSum((a&b)<<1, a^b);}
};

迭代解法：

class Solution {
public:int getSum(int a, int b) {int carry = 0;while (a != 0) {carry = (a & b) << 1;b = a ^ b;a = carry;            }return b;}
};

python版本：不明白 ~(a ^ mask) 是。。。

class Solution(object):def getSum(self, a, b):""":type a: int:type b: int:rtype: int"""# 32 bits integer maxMAX = 0x7FFFFFFF# 32 bits interger minMIN = 0x80000000# mask to get last 32 bitsmask = 0xFFFFFFFFwhile b != 0:# ^ get different bits and & gets double 1s, << moves carrya, b = (a ^ b) & mask, ((a & b) << 1) & mask# if a is negative, get a's 32 bits complement positive first# then get 32-bit positive's Python complement negativereturn a if a <= MAX else ~(a ^ mask)

转载于:https://www.cnblogs.com/bonelee/p/8593090.html

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