Python練手之根據前序和中序&根據中序和後序重建二叉樹，輸出前序、中序和後序遍歷結果

這是根據本人另一個C語言版本採用python實現的，添加了根據中序和後序重建二叉樹功能，更多詳細解釋可參考：http://blog.csdn.net/hinyunsin/archive/2011/04/11/6315502.aspx

 

下面就是python代碼：

#-*- coding: utf-8 -*- #!/usr/bin/python #Filename: BTreeNode.py ''' Created on 2011-4-11 @author: boyce @contact: [e-mail] @version: 1.0 ''' class BTree: ''' Represent a no in a binary tree. ''' def __init__(self, c='/0', l=None, r=None): ''' Initializes the node's data ''' self.e = c self.left = l self.right = r def preorderTraverse(bt): ''' 返回前序遍歷結果 ''' if bt: return '%s%s%s' % (bt.e, preorderTraverse(bt.left), preorderTraverse(bt.right)) return '' def inorderTraverse(bt): ''' 返回中序遍歷結果 ''' if bt: return '%s%s%s' % (inorderTraverse(bt.left), bt.e, inorderTraverse(bt.right)) return ''; def postorderTraverse(bt): ''' 返回後序遍歷結果 ''' if bt: return '%s%s%s' % (postorderTraverse(bt.left), postorderTraverse(bt.right), bt.e) return '' def printBTree(bt, depth): ''' 遞歸打印這棵二叉樹，*號表示該節點爲NULL ''' ''' if not bt: ch = '*' else: ch = bt.e ''' #ch=(lambda x: (x and x.e) or '*')(bt) ch = bt.e if bt else '*' if(depth > 0): print '%s%s%s' % ((depth - 1) * ' ', '--', ch) else: print ch if not bt: return printBTree(bt.left, depth + 1) printBTree(bt.right, depth + 1) def buildBTreeFromPreIn(preo, ino): ''' 根據前序和中序遍歷結果重構這棵二叉樹 ''' if(preo == '' or ino == ''): return None pos = ino.find(preo[0]) if(pos < 0): return None return BTree(preo[0], buildBTreeFromPreIn(preo[1:pos + 1], ino[0:pos]), buildBTreeFromPreIn(preo[pos + 1:], ino[pos + 1:])) #return nd def buildBTreeFromInPost(ino, po): ''' 根據中序和後序遍歷結果重構這棵二叉樹 ''' if(ino == '' or po == ''): return None pos = ino.find(po[-1]) if(pos < 0): return None return BTree(po[-1], buildBTreeFromInPost(ino[0:pos], po[0:pos]), buildBTreeFromInPost(ino[pos + 1:], po[pos:-1])) if __name__ == '__main__': preo = 'ABDGCEFH' ino = 'DGBAECHF' po = 'GDBEHFCA' bt = buildBTreeFromPreIn(preo, ino) print 'Build from preorder & inorder' print 'Preorder: %s' % (preorderTraverse(bt)) print 'Inorder: %s' % (inorderTraverse(bt)) print 'Postorder: %s' % (postorderTraverse(bt)) print 'The BTree is (* means no such a node):' printBTree(bt, 0) bt = buildBTreeFromInPost(ino, po) print 'Build from inorder & postorder' print 'Preorder: %s' % (preorderTraverse(bt)) print 'Inorder: %s' % (inorderTraverse(bt)) print 'Postorder: %s' % (postorderTraverse(bt)) print 'The BTree is (* means no such a node):' printBTree(bt, 0)

python確實很有意思，寫出來的東西比c要簡潔很多，當然，我的其實還遠遠不夠簡潔，沒辦法，還是新手嘛，呵呵~

這裏多了根據中序和後序重建二叉樹功能，原理和根據前序和中序重建一樣。

 

下面是執行結果：