先用python的類表示二叉樹的節點:
class Node(object):
def __init__(self, root=None, ltree=None, rtree=None):
self.root = root
self.ltree = ltree
self.rtree = rtree
訪問樹的所有結點,有且僅訪問一次。按照根節點位置的不同分爲前序遍歷,中序遍歷,後序遍歷。
前序遍歷:根節點->左子樹->右子樹
中序遍歷:左子樹->根節點->右子樹
後序遍歷:左子樹->右子樹->根節點
不同的遍歷方式分別對應的python函數實現爲:
def pretraverse(tree):
if tree == None:
return
print(tree.root, end='')
pretraverse(tree.ltree)
pretraverse(tree.rtree)
def midtraverse(tree):
if tree == None:
return
midtraverse(tree.ltree)
print(tree.root, end='')
midtraverse(tree.rtree)
def aftertraverse(tree):
if tree == None:
return
aftertraverse(tree.ltree)
aftertraverse(tree.rtree)
print(tree.root, end='')
有個二叉樹舉例如下:
輸出結果爲:
if __name__ == '__main__':
tree = Node('a', Node('b', Node('d', rtree=Node('e')), Node('f', ltree=Node('g'))), Node('c'))
pretraverse(tree)
print('\n')
midtraverse(tree)
print('\n')
aftertraverse(tree)
abdefgc
debgfac
edgfbca