Palindrome Permutation II
Problem: Palindrome Permutation II
We can first establish a dictionary for characters to judge whether the word can form a permutation and find the single character if there's such one. Then we can use backtracking to construct a palindrome. There's another solution here using swapping to construct permutation.
Code in Python:
# 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 levelOrderBottom(self, root):
"""
:type root: TreeNode
:rtype: List[List[int]]
"""
if not root: return []
res = []
level = [root]
while level:
res = [level] + res
next = []
for node in level:
if node.left: next.append(node.left)
if node.right: next.append(node.right)
level = next
return res