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Merge pull request #316 from AnshulMalik/segment-tree-refactor

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refactor-segment-tree
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Christian Bender 2018-07-22 18:04:58 +02:00 committed by GitHub
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1 changed files with 34 additions and 28 deletions
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data_structures/Binary Tree/SegmentTree.py
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@ -3,63 +3,69 @@ import math
class SegmentTree: class SegmentTree:
def __init__(self, N): def __init__(self, A):
self.N = N self.N = len(A)
self.st = [0 for i in range(0,4*N)] # approximate the overall size of segment tree with array N self.st = [0] * (4 * self.N) # approximate the overall size of segment tree with array N
self.build(1, 0, self.N - 1)
def left(self, idx): def left(self, idx):
return idx*2 return idx * 2
def right(self, idx): def right(self, idx):
return idx*2 + 1 return idx * 2 + 1
def build(self, idx, l, r, A): def build(self, idx, l, r):
if l==r: if l == r:
self.st[idx] = A[l-1] self.st[idx] = A[l]
else : else:
mid = (l+r)//2 mid = (l + r) // 2
self.build(self.left(idx),l,mid, A) self.build(self.left(idx), l, mid)
self.build(self.right(idx),mid+1,r, A) self.build(self.right(idx), mid + 1, r)
self.st[idx] = max(self.st[self.left(idx)] , self.st[self.right(idx)]) self.st[idx] = max(self.st[self.left(idx)] , self.st[self.right(idx)])
def update(self, idx, l, r, a, b, val): # update(1, 1, N, a, b, v) for update val v to [a,b] def update(self, a, b, val):
return self.update_recursive(1, 0, self.N - 1, a - 1, b - 1, val)
def update_recursive(self, idx, l, r, a, b, val): # update(1, 1, N, a, b, v) for update val v to [a,b]
if r < a or l > b: if r < a or l > b:
return True return True
if l == r : if l == r :
self.st[idx] = val self.st[idx] = val
return True return True
mid = (l+r)//2 mid = (l+r)//2
self.update(self.left(idx),l,mid,a,b,val) self.update_recursive(self.left(idx), l, mid, a, b, val)
self.update(self.right(idx),mid+1,r,a,b,val) self.update_recursive(self.right(idx), mid+1, r, a, b, val)
self.st[idx] = max(self.st[self.left(idx)] , self.st[self.right(idx)]) self.st[idx] = max(self.st[self.left(idx)] , self.st[self.right(idx)])
return True return True
def query(self, idx, l, r, a, b): #query(1, 1, N, a, b) for query max of [a,b] def query(self, a, b):
return self.query_recursive(1, 0, self.N - 1, a - 1, b - 1)
def query_recursive(self, idx, l, r, a, b): #query(1, 1, N, a, b) for query max of [a,b]
if r < a or l > b: if r < a or l > b:
return -math.inf return -math.inf
if l >= a and r <= b: if l >= a and r <= b:
return self.st[idx] return self.st[idx]
mid = (l+r)//2 mid = (l+r)//2
q1 = self.query(self.left(idx),l,mid,a,b) q1 = self.query_recursive(self.left(idx), l, mid, a, b)
q2 = self.query(self.right(idx),mid+1,r,a,b) q2 = self.query_recursive(self.right(idx), mid + 1, r, a, b)
return max(q1,q2) return max(q1, q2)
def showData(self): def showData(self):
showList = [] showList = []
for i in range(1,N+1): for i in range(1,N+1):
showList += [self.query(1, 1, self.N, i, i)] showList += [self.query(i, i)]
print (showList) print (showList)
if __name__ == '__main__': if __name__ == '__main__':
A = [1,2,-4,7,3,-5,6,11,-20,9,14,15,5,2,-8] A = [1,2,-4,7,3,-5,6,11,-20,9,14,15,5,2,-8]
N = 15 N = 15
segt = SegmentTree(N) segt = SegmentTree(A)
segt.build(1,1,N,A) print (segt.query(4, 6))
print (segt.query(1,1,N,4,6)) print (segt.query(7, 11))
print (segt.query(1,1,N,7,11)) print (segt.query(7, 12))
print (segt.query(1,1,N,7,12)) segt.update(1,3,111)
segt.update(1,1,N,1,3,111) print (segt.query(1, 15))
print (segt.query(1,1,N,1,15)) segt.update(7,8,235)
segt.update(1,1,N,7,8,235)
segt.showData() segt.showData()