need to compare list elemets in one to one manner

I'm having the list in which I want to map elements in it in one to one manner (the parameters are present in the list)

For eg:

                Int sum(int a,int b,int  c);                                              //old

                Int sum(int a,int b,int  c);                                              //new

If I compare this there is no problem but

                Int sum(int a,int b,int  c);                                              //old

                Int sum(int a,int b);                                                         //new

But if I compare this there is a problem as I cannot map one to one elements.

I need  that 'int a' of old must get compared with 'int a' of the new.

Give me some solution fast…