# 【LeetCode】662. Maximum Width of Binary Tree 解题报告（Python）

# 题目描述：

Given a binary tree, write a function to get the maximum width of the given tree. The width of a tree is the maximum width among all levels. The binary tree has the same structure as a full binary tree, but some nodes are null.

The width of one level is defined as the length between the end-nodes (the leftmost and right most non-null nodes in the level, where the null nodes between the end-nodes are also counted into the length calculation.

``````Example 1:
Input:

1
/   \
3     2
/ \     \
5   3     9

Output: 4
Explanation: The maximum width existing in the third level with the length 4 (5,3,null,9).

Example 2:
Input:

1
/
3
/ \
5   3

Output: 2
Explanation: The maximum width existing in the third level with the length 2 (5,3).

Example 3:
Input:

1
/ \
3   2
/
5

Output: 2
Explanation: The maximum width existing in the second level with the length 2 (3,2).

Example 4:
Input:

1
/ \
3   2
/     \
5       9
/         \
6           7
Output: 8
Explanation:The maximum width existing in the fourth level with the length 8 (6,null,null,null,null,null,null,7).
``````

Note: Answer will in the range of 32-bit signed integer.

# 解题方法

``````# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
def widthOfBinaryTree(self, root):
"""
:type root: TreeNode
:rtype: int
"""
queue = collections.deque()
queue.append((root, 1))
res = 0
while queue:
width = queue[-1][1] - queue[0][1] + 1
res = max(width, res)
for _ in range(len(queue)):
n, c = queue.popleft()
if n.left: queue.append((n.left, c * 2))
if n.right: queue.append((n.right, c * 2 + 1))
return res
``````

# 日期

2018 年 3 月 21 日 ———— 啊，耽误了一天没刷题。。