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Tags: 每日算法题, 算法, 数据结构, 面试题, Daily Interview Problem, Data Structures and Algorithms, Computer Programming, Python, | English | Home Page | Category: Computing | 220 Views, 16255 Search Bots | 135 Words
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Hi, here's your problem today. This problem was recently asked by Microsoft:
A unival tree is a tree where all the nodes have the same value. Given a binary tree, return the number of unival subtrees in the tree.
For example, the following tree should return 5:
The 5 trees are:
- The three single '1' leaf nodes. (+3)
- The single '0' leaf node. (+1)
- The [1, 1, 1] tree at the bottom. (+1)
Here's a starting point:
Tags: 每日算法题, 算法, 数据结构, 面试题, Daily Interview Problem, Data Structures and Algorithms, Computer Programming, Python, | English | Home Page | Cateogry: Computing | 220 Views, 16255 Search Bots | 135 Words A unival tree is a tree where all the nodes have the same value. Given a binary tree, return the number of unival subtrees in the tree.
For example, the following tree should return 5:
0
/ \
1 0
/ \
1 0
/ \
1 1
The 5 trees are:
- The three single '1' leaf nodes. (+3)
- The single '0' leaf node. (+1)
- The [1, 1, 1] tree at the bottom. (+1)
Here's a starting point:
class Node(object):
def __init__(self, val):
self.val = val
self.left = None
self.right = None
def count_unival_subtrees(root):
# Fill this in.
a = Node(0)
a.left = Node(1)
a.right = Node(0)
a.right.left = Node(1)
a.right.right = Node(0)
a.right.left.left = Node(1)
a.right.left.right = Node(1)
print count_unival_subtrees(a)
# 5
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