leetcode

Solution to some Leetcode problems written in C++
git clone git://git.dimitrijedobrota.com/leetcode.git
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0065.cpp (1428B)

      1 class Solution {
      2     using it_t = string::const_iterator;
      3 
      4     static bool validSign(it_t &pos, const it_t &end) {
      5         if (*pos == '-' || *pos == '+') {
      6             pos++;
      7             if (find(pos, end, '-') != end || find(pos, end, '+') != end) {
      8                 return false;
      9             }
     10         }
     11 
     12         return pos != end;
     13     }
     14 
     15     static bool validDigit(const it_t &pos, const it_t &end) {
     16         return all_of(pos, end, [](char c) { return isdigit(c); });
     17     }
     18 
     19     static bool isDecimal(const string &s) {
     20         auto pos = begin(s);
     21 
     22         if (!validSign(pos, end(s))) return false;
     23         if (string(pos, end(s)) == ".") return false;
     24 
     25         auto dot = find(pos, end(s), '.');
     26         return validDigit(pos, dot) && validDigit(dot + 1, end(s));
     27     }
     28 
     29     static bool isInteger(const string &s) {
     30         auto pos = begin(s);
     31         if (!validSign(pos, end(s))) return false;
     32         return validDigit(pos, end(s));
     33     }
     34 
     35   public:
     36     bool isNumber(const string &s) const {
     37         auto e = s.find('e'), E = s.find('E');
     38 
     39         if (E != string::npos) swap(e, E);
     40         if (e != string::npos) {
     41             const string first = s.substr(0, e);
     42             const string second = s.substr(e + 1);
     43             return !first.empty() && !second.empty() && isInteger(second) &&
     44                    (isDecimal(first) || isInteger(first));
     45         }
     46 
     47         return isDecimal(s) || isInteger(s);
     48     }
     49 };