65.Valid Number
https://leetcode.com/problems/valid-number/discuss/23738/Clear-Java-solution-with-ifs
https://leetcode.com/problems/valid-number/discuss/23762/A-simple-solution-in-cpp
https://leetcode.com/problems/valid-number/discuss/23738/Clear-Java-solution-with-ifs
https://leetcode.com/problems/valid-number/discuss/23762/A-simple-solution-in-cpp