Stacks for Languages

Write a method bool inLanguage(char* theString) that uses one stack to determine whether theString has the same number of A's as B's. If the string contains anything other than A or B (capital A or capital B), return false.

Sample Input 1:

ABBA 

Sample Output 1:

true 

Sample Input 2:

ABABB

Sample Output 2:

false

Sample Input 3:

BABAAB

Sample Output 3:

true

Sample Input 4:

ABC

Sample Output 4:

false

Sample Input 5:

BBAAA

Sample Output 5:

false