Please solve the following question using C++, without any library except for and .

3.4 Converting base representation. Write a function convertbase which converts a number, represented as a string in one base, to a new string representing that number in a new base. You may assume that the number can be stored in an int without overflow string convertbase (const string& numstr, const int frombase, const int tobase) The character to digitvalue+'0" represent a digit with value digit value is the ASCII character The values of frombase and tobase will always be in the range 2 to 200 inclusive