371 sum of two integers
371. Sum of Two Integers
题目: https://leetcode.com/problems/sum-of-two-integers/
难度:
Easy
思路
谷歌答案
位运算
XOR
x y output
0 0 0
1 0 1
0 1 1
1 1 0
AND
x y output
0 0 0
1 0 1
0 1 1
1 1 1
如果对x和y来做加法（x和y都是一位的），那么末位会是x xor y，进位会是x and y
python没有左移，用c++来看
class Solution {
public:
int getSum(int a, int b) {
while (b != 0 ){
int c = a & b;
a = a ^ b;
b = c << 1;
}
return a;
}
};
实际上看到答案还是没有那么明白的，还是动手算算
a = 6 (0110)
b = 15 (1111)
1st
---------
carry = a & b = 0110
a = a ^ b = 1001
b = 1100
2nd
---------
carry = a & b = 1000
a = a ^ b = 0101
b = 10000
3rd
----------
carry = a & b = 0
a = a ^ b = 10101
b = 0
这个时候a 的值是2^4 + 2^2 + 2^0 = 16+4+1 = 21
虽然convence了我自己，但是表示依旧迷茫ing
也知道位运算需要待补啊
