The ingenious application of the position arithmetic of the interview question

1, judge whether a number is 2 of the n-th square
Title: Use an expression to determine whether a number x is 2 of the n-th square, that is, 2,4,8,16 ... And so on, it is not possible to use circular statements.
Parsing: 2,4,8,16 Such a number translates into binary is 10,100,1000,10000.

if x is minus 1 (the lower one and each bit of the binary is 1), this number is done with X, and if the answer is 0, then X is the n-th of the 2.

2, two number of exchanges
Title: The value of a A, a, two number is exchanged, and no intermediate variables are used.
Solution 1:
A = A+b;
b = a A;
A = a-B;
Solution 2: Use XOR or bitwise operation.
XOR operation: The same is 0, the difference is 1.
A = a^b;//a becomes a result of the same 0, which differs from 1
b = a^b;//The result and b do the operation, get the original A
A = a^b;//The result and a do the operation, get the original B