Please tell me the logic for the code.

general
1

For eg. 2341 then we subtract the adjacent terms with each 2-3=1
2-4=1
4-1=3
then after subtracting we get :113
then we minus 1-1=0
1-3=2
that is the single term which is 2 this must be the answer.
Please tell the Logic For code

2

Keep generating the last and the second last digits of the number and subtract them. Use the resultant to form a new number. Once the new number has been formed, repeat the above steps with the new number until we get a single digit new number. That must be the answer.
For eg. 2341, on generating the last and the second last digits of the number and subtracting them, we get,
4-1=3
3-4=1
2-3=1
The new number formed is 113. Repeating the above steps with 113 we get,
1-3=2
1-1=0
The new number formed is 2 which is a single digit number and thus the answer.