C++ use of data structures please

Closest Common Ancestor David has found out his family tree at home and the family tree is a rooted-tree. David is interested in finding out the closest common ancestor of two members in this tree. However, the tree is too complicated. David knows that he could use a lot of time to find out the entire closest common ancestor for those interesting pairs. Can you help David to create a program to find out the closest common ancestor quickly? For this question, the ancestor can be the member itself. So, the ancestor of the root member is itself. Input For simplicity, this question uses one non-zero positive integer (the integer is less than or equal to the number of members N) to indicate a family member in the tree. The input contains T test cases (O*T