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#
#
# Nim's Runtime Library
# (c) Copyright 2012 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
# not really an AVL tree anymore, but still balanced ...
template isBottom(n: PAvlNode): bool = n == bottom
proc lowGauge(n: PAvlNode): int =
var it = n
while not isBottom(it):
result = it.key
it = it.link[0]
proc highGauge(n: PAvlNode): int =
result = -1
var it = n
while not isBottom(it):
result = it.upperBound
it = it.link[1]
proc find(root: PAvlNode, key: int): PAvlNode =
var it = root
while not isBottom(it):
if it.key == key: return it
it = it.link[ord(it.key <% key)]
proc inRange(root: PAvlNode, key: int): PAvlNode =
var it = root
while not isBottom(it):
if it.key <=% key and key <% it.upperBound: return it
it = it.link[ord(it.key <% key)]
proc skew(t: var PAvlNode) =
if t.link[0].level == t.level:
var temp = t
t = t.link[0]
temp.link[0] = t.link[1]
t.link[1] = temp
proc split(t: var PAvlNode) =
if t.link[1].link[1].level == t.level:
var temp = t
t = t.link[1]
temp.link[1] = t.link[0]
t.link[0] = temp
inc t.level
proc add(a: var MemRegion, t: var PAvlNode, key, upperBound: int) {.benign.} =
if t == bottom:
t = allocAvlNode(a, key, upperBound)
else:
if key <% t.key:
add(a, t.link[0], key, upperBound)
elif key >% t.key:
add(a, t.link[1], key, upperBound)
else:
sysAssert false, "key already exists"
skew(t)
split(t)
proc del(a: var MemRegion, t: var PAvlNode, x: int) {.benign.} =
if t == bottom: return
a.last = t
if x <% t.key:
del(a, t.link[0], x)
else:
a.deleted = t
del(a, t.link[1], x)
if t == a.last and a.deleted != bottom and x == a.deleted.key:
a.deleted.key = t.key
a.deleted.upperBound = t.upperBound
a.deleted = bottom
t = t.link[1]
deallocAvlNode(a, a.last)
elif t.link[0].level < t.level-1 or
t.link[1].level < t.level-1:
dec t.level
if t.link[1].level > t.level:
t.link[1].level = t.level
skew(t)
skew(t.link[1])
skew(t.link[1].link[1])
split(t)
split(t.link[1])
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