Why is insertion into my tree faster on sorted input than random input?

Question

Now I\'ve always heard binary search trees are faster to build from randomly selected data than ordered data, simply because ordered data requires explicit rebalancing to keep t

Answer 1

Yes it's the number of rotations that is causing the extra time. Here's what I did:

• Remove the lines checking priority in HeapifyLeft and HeapifyRight so rotations are always done.
• Added a Console.WriteLine after the if in RotateLeft and RotateRight.
• Added a Console.WriteLine in the IsEmpty part of the Insert method to see what was being inserted.
• Ran the test once with 5 values each.

Output:

TimeIt(5, RandomInsert)
Inserting 0.593302943554382
Inserting 0.348900582338171
RotateRight
Inserting 0.75496212381635
RotateLeft
RotateLeft
Inserting 0.438848891499848
RotateRight
RotateLeft
RotateRight
Inserting 0.357057290783644
RotateLeft
RotateRight

TimeIt(5, OrderedInsert)
Inserting 0.150707998383189
Inserting 1.58281302712057
RotateLeft
Inserting 2.23192588297274
RotateLeft
Inserting 3.30518679009061
RotateLeft
Inserting 4.32788012657682
RotateLeft

Result: 2 times as many rotations on random data.