make findMedianNumber compilable, need debug.

Signed-off-by: Wayne Wang <wythern@gmail.com>
Update findMedianNumber.

1. Add test.
2. Actually it returns the merged_array[(m+n-1)/2] element.
3. Will change to official median number definition in next version.

Signed-off-by: Wayne Wang <wythern@gmail.com>
Update findMedianNumber.

Accepted

Signed-off-by: Wayne Wang <wythern@gmail.com>
Add AddTwoNumbers.cpp

Accepted.
The last carry is a trap.

Signed-off-by: Wayne Wang <wythern@gmail.com>