Bug in the solution to measure the perimter of a skyline

[GoogleCodeExporter]

What steps will reproduce the problem?

1.
Input:
0 4 1
1 1 1
2 1 2

What is the expected output? What do you see instead?
The result should be: 8
The actual result is:  10

Version:
http://ideone.com/oYg0Fq

Please provide any additional information below.
It looks like there's a bug while removing the element from the bst when two or 
more elements have the same height

Original issue reported on code.google.com by vdeantoni on 25 Mar 2013 at 7:28