Just a small trick to swap two variables without using the third variable.
Here we go...
Consider the following example
1) int i =10
2) int j=15
3) i=i+j which is 10+15 making it 25. Now, i=25
4) j=i-j which is 25-15 making j=10
5) i=i-j which is 25-10 making i=15
So, you see that following are the values of both i & j after performing above code logic
i=15 and j=10
Hope this trick helps in any of the scenario