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ufarray.py
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ufarray.py
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# Array based union find data structure
# P: The array, which encodes the set membership of all the elements
class UFarray:
def __init__(self):
# Array which holds label -> set equivalences
self.P = []
# Name of the next label, when one is created
self.label = 0
def makeLabel(self):
r = self.label
self.label += 1
self.P.append(r)
return r
# Makes all nodes "in the path of node i" point to root
def setRoot(self, i, root):
while self.P[i] < i:
j = self.P[i]
self.P[i] = root
i = j
self.P[i] = root
# Finds the root node of the tree containing node i
def findRoot(self, i):
while self.P[i] < i:
i = self.P[i]
return i
# Finds the root of the tree containing node i
# Simultaneously compresses the tree
def find(self, i):
root = self.findRoot(i)
self.setRoot(i, root)
return root
# Joins the two trees containing nodes i and j
# Modified to be less agressive about compressing paths
# because performance was suffering some from over-compression
def union(self, i, j):
if i != j:
root = self.findRoot(i)
rootj = self.findRoot(j)
if root > rootj: root = rootj
self.setRoot(j, root)
self.setRoot(i, root)
def flatten(self):
for i in range(1, len(self.P)):
self.P[i] = self.P[self.P[i]]
def flattenL(self):
k = 1
for i in range(1, len(self.P)):
if self.P[i] < i:
self.P[i] = self.P[self.P[i]]
else:
self.P[i] = k
k += 1