python實現(xiàn)的二叉樹算法和kmp算法實例
主要是:前序遍歷、中序遍歷、后序遍歷、層級遍歷、非遞歸前序遍歷、非遞歸中序遍歷、非遞歸后序遍歷
#!/usr/bin/env python
#-*- coding:utf8 -*-
class TreeNode(object):
def __init__(self, data=None, left=None, right=None):
self.data = data
self.left = left
self.right = right
class Tree(object):
def __init__(self, root=None):
self.root = None
def makeTree(self, data, left, right):
self.root = TreeNode(data, left, right)
def is_empty(self):
"""是否為空 """
if self.root is None:
return True
return False
def preOrder(self, r):
"""前序遍歷 """
if not r.is_empty():
print r.root.data
if r.root.left is not None:
r.preOrder(r.root.left)
if r.root.right is not None:
r.preOrder(r.root.right)
def inOrder(self, r):
"""中序遍歷 """
if not r.is_empty():
if r.root.left is not None:
r.preOrder(r.root.left)
print r.root.data
if r.root.right is not None:
r.preOrder(r.root.right)
def postOrder(self, r):
"""后續(xù)遍歷 """
if not r.is_empty():
if r.root.left is not None:
r.preOrder(r.root.left)
print r.root.data
if r.root.right is not None:
r.preOrder(r.root.right)
def levelOrder(self, r):
"""層級遍歷 """
if not r.is_empty():
s = [r]
while len(s) > 0:
temp = s.pop(0) # 先彈出最先append到的點
if temp and temp.root is not None:
print temp.root.data
if temp.root.left is not None:
s.append(temp.root.left)
if self.root.right is not None:
s.append(temp.root.right)
def preOrder1(self, r):
"""非遞歸 前序遍歷 """
stack = []
current = r
while len(stack) > 0 or (current and not current.is_empty()):
while current and not current.is_empty():
print current.root.data
stack.append(current)
current = current.root.left
if len(stack) > 0:
current = stack.pop()
current = current.root.right
def inOrder1(self, r):
"""非遞歸 中序遍歷 """
stack = []
current = r
while len(stack) > 0 or (current and not current.is_empty()):
while current and not current.is_empty():
stack.append(current)
current = current.root.left
if len(stack) > 0:
current = stack.pop()
print current.root.data
current = current.root.right
def postOrder1(self, r):
"""非遞歸 后續(xù)遍歷 """
stack = []
current = r
pre = None
while len(stack) > 0 or (current and not current.is_empty()):
if current and not current.is_empty():
stack.append(current)
current = current.root.left
elif stack[-1].root.right != pre:
current = stack[-1].root.right
pre = None
else:
pre = stack.pop()
print pre.root.data
def leaves_count(self, r):
"""求葉子節(jié)點個數(shù) """
if r.is_empty():
return 0
elif (not r.root.left) and (not r.root.right):
return 1
else:
return r.root.left.leaves_count(r.root.left) + r.root.right.leaves_count(r.root.right)
if __name__ == '__main__':
"""二叉樹"""
ra, rb, rc, rd, re, rf = Tree(), Tree(), Tree(), Tree(), Tree(), Tree()
ra.makeTree("a", None, None)
rb.makeTree("b", None, None)
rc.makeTree("c", None, None)
rd.makeTree("d", None, None)
re.makeTree("e", None, None)
rf.makeTree("f", None, None)
r1, r2, r3, r4, r = Tree(), Tree(), Tree(), Tree(), Tree()
r1.makeTree("-", rc, rd)
r2.makeTree("*", rb, r1)
r3.makeTree("+", ra, r2)
r4.makeTree("/", re, rf)
r.makeTree("-", r3, r4)
r.preOrder(r)
r.inOrder(r)
r.postOrder(r)
r.levelOrder(r)
print r.leaves_count(r)
大學的時候學過kmp算法,最近在看的時候發(fā)現(xiàn)竟然忘了,所以去重新看了看書,然后用python寫下了這個算法:
def kmp(text, pattern):
"""kmp算法 """
pattern = list(pattern)
next = [-1] * len(pattern)
#next 函數(shù)
i, j = 1, -1
for i in range(1, len(pattern)):
j = next[i - 1]
while True:
if pattern[i - 1] == pattern[j] or j == -1:
next[i] = j + 1
break
else:
j = next[j]
#循環(huán)比較
i, j = 0, 0
while i < len(text) and j < len(pattern):
if text[i] == pattern[j] or j == -1:
i += 1
j += 1
else:
j = next[j]
#返回結果 如果匹配,返回匹配的位置,否則返回-1
if j == len(pattern):
print i – j
else:
print -1
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