Add solution for 2015 Day 19

src/common/lib/Helper.h

@@ -49,9 +49,9 @@ struct Helper
     t.erase(std::remove_if(t.begin(), t.end(), func), t.end());
   }
 
-  static bool StartsWith(const std::string_view& str, const std::string& prefix)
+  static bool StartsWith(const std::string_view& str, const std::string& prefix, size_t offset = 0)
   {
-    return str.substr(0, prefix.size()) == prefix;
+    return str.substr(offset, prefix.size()) == prefix;
   }
 
   static bool EndsWith(const std::string_view& str, const std::string& prefix)
@@ -59,6 +59,11 @@ struct Helper
     return str.substr(str.size() - prefix.size(), prefix.size()) == prefix;
   }
 
+  static void Replace(std::string& str, size_t size, const std::string& other, size_t pos)
+  {
+    str.replace(pos, size, other);
+  }
+
   static bool IsDigit(char c)
   {
     return c >= '0' && c <= '9';