LintCode:等价二叉树

LintCode:等价二叉树

如果一棵树前、中、后序遍历结果都一样的话肯定就是等价的了。

""" Definition of TreeNode: class TreeNode: def __init__(self, val): this.val = val this.left, this.right = None, None """
class Solution:
    """ @param a, b, the root of binary trees. @return true if they are identical, or false. """
    def isIdentical(self, a, b):
        # Write your code here
        if a == None and b == None:
            return True
        if (a == None and b != None) or (a != None and b == None):
            return False
        L = []
        L1 = self.pre_order(a, L) + self.mid_order(a, L) + self.last_order(a, L)
        L = []
        L2 = self.pre_order(b, L) + self.mid_order(b, L) + self.last_order(b, L)
        if L1 == L2:
            return True
        return False

    def pre_order(self, root, L):
        if root == None:
            return
        L.append(root.val)
        self.pre_order(root.left, L)
        self.pre_order(root.right, L)
        return L

    def mid_order(self, root, L):
        if root == None:
            return
        self.mid_order(root.left, L)
        L.append(root.val)
        self.mid_order(root.right, L)
        return L

    def last_order(self, root, L):
        if root == None:
            return
        self.mid_order(root.left, L)
        self.mid_order(root.right, L)
        L.append(root.val)
        return L