前序，中序，后序，层序

Author: LockGit

README.md

@@ -534,3 +534,14 @@ pip install matplotlib
 ```
 ![](https://github.com/LockGit/Py/blob/master/img/svm.png)
 
+
+### (前序，中序，后序，层序) btree.py
+```
+➜  Py git:(master) ✗ python btree.py
+前序遍历： root A C D F G B E
+中序遍历： C F D G A root B E
+后序遍历： F G D C A E B root
+层序遍历： root A B C E D F G
+构造树结构如下图
+```
+![](https://github.com/LockGit/Py/blob/master/img/btree.png)

btree.py

@@ -0,0 +1,85 @@
+#!/usr/bin/env python
+# encoding: utf-8
+# author: Lock
+# time: 2018/1/24 00:38
+class BTree:
+    def __init__(self, value):
+        self.left = None
+        self.data = value
+        self.right = None
+
+    def insertLeft(self, value):
+        self.left = BTree(value)
+        return self.left
+
+    def insertRight(self, value):
+        self.right = BTree(value)
+        return self.right
+
+    def show(self):
+        print self.data,
+
+
+def preorder(node):
+    if node.data:
+        node.show()
+        if node.left:
+            preorder(node.left)
+        if node.right:
+            preorder(node.right)
+
+
+def inorder(node):
+    if node.data:
+        if node.left:
+            inorder(node.left)
+        node.show()
+        if node.right:
+            inorder(node.right)
+
+
+def postorder(node):
+    if node.data:
+        if node.left:
+            postorder(node.left)
+        if node.right:
+            postorder(node.right)
+        node.show()
+
+
+def layerorder(node):
+    stack = [node]
+    while len(stack):
+        	node = stack.pop(0)
+        	if node.data:
+        		node.show()
+	        if node.left:
+	            stack.append(node.left)
+	        if node.right:
+	        	stack.append(node.right)
+
+
+if __name__ == "__main__":
+    Root = BTree("root")
+    A = Root.insertLeft("A")
+    C = A.insertLeft("C")
+    D = C.insertRight("D")
+    F = D.insertLeft("F")
+    G = D.insertRight("G")
+    B = Root.insertRight("B")
+    E = B.insertRight("E")
+
+    print "前序遍历：",
+    preorder(Root)
+
+    print ""
+    print "中序遍历：",
+    inorder(Root)
+
+    print ""
+    print "后序遍历：",
+    postorder(Root)
+
+    print ""
+    print "层序遍历：",
+    layerorder(Root)