Counting Bits
问题描述（难度中等）Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1’s in their binary representa
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Palindromic Substrings
问题描述（难度中等）given a string, your task is to count how many palindromic substrings in this string.
The substrings with different start indexes or end ind
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Lowest Common Ancestor of a Binary Tree
问题描述（难度中等）Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
According to the definition of LCA on Wikipedia:
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Palindrome Linked List
问题描述（难度简单）Given a singly linked list, determine if it is a palindrome.
Example 1:
12Input: 1->2Output: false
Example 2:
12Input: 1->2->2->
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Sort List
问题描述（难度中等）Sort a linked list in O(n log n) time using constant space complexity.
Example 1:
12Input: 4->2->1->3Output: 1->2->3->4
Ex
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