BM318Maximum Product of Word Lengths

思路1 Brute Force

• Use brute force two check every pairs. Has TLE problem

思路2 Bit

• I want to use Bit, but bit of a and bit of bb always have common 1s with intersection or xor. I have no idea how to use them.
• Then I found some code use _char - ‘a’ and then to use bit.