message: Update excel-sheet-column-number.cpp solution2
diff: @@ -12,3 +12,16 @@ public:
  return number;
  }
  };
  +
  +// Time: O(n)
  +// Space: O(1)
  +
  +class Solution2 {
  + public:
  + int titleToNumber(string s) {
  + return accumulate(s.begin(), s.end(), 0,
  + [](int sum, char c) {
  + return sum * 26 + c - 'A' + 1;
  + });
  + }
  +};
  