题目：Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.
Note:
The given integer is guaranteed to fit within the range of a 32-bit signed integer.You could assume no leading zero bit in the integer’s binary representation.题解：题意是将一个数变成其二进制数，然后将其位为0变为1，位为1变为0，然后将其输出。例如5位101，变为010，则输出2，联想到010=111-101（异或也行）.即可变为求任何数变为二进制数并将其位为0的全部变为1，有两种方法，一种是逐位or 1,或者是考虑111=1000-1，下面用代码体现。
代码1：
class Solution { public: int findComplement(int num) { int i; int c=num; bool start=false; for(i=31;i>=0;i--) { if(c&(1<<i)) start=true; if(start) c=c|(1<<i); } return (c-num); } };代码2： class Solution { public: int findComplement(int num) { int mask=1; int c=num; while(c){ c>>=1; mask<<=1; } return ((mask-1)^num); } };
