Can you please provide me test cases where i can fail?

My code is here:
http://www.ideone.com/396m3

see the second sample on your site.

the answer is 2.

Any suggestions on improvement of the algorithm i use?
Is my approach wrong or can be fine with some tweaking?

Ravi Kiran.

If in your current state s1[i]==s2[j], you should not assume states i+1,j and i,j+1. Only i+1,j+1.

Thanks a lot everyone.
I got accepted with the change you suggested.