左移右移的能够使得数字*2或者/2
那*3怎么办,就左移一位然后再+
经典面试题:
1.交换2个数,不用temp a=10 b=12
1.1
a = a + b = 22
b = a - b = 10
a = a - b =10
1.2 位运算 ^(异或)
a=1010 b = 1100
a = a ^ b =0110
b = a ^ b =1010
a = a ^ b = 1100
