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摘要： Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree [1,2,2,3,4,4,3] is symmet 阅读全文

摘要： Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists. 思路： 由于链表 阅读全文

摘要： Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST. 思路：利用快慢指针找到中间节点，作为根节点，然后左子树即为左边链表部分，右子树即 阅读全文

摘要： We define the Perfect Number is a positive integer that is equal to the sum of all its positive divisors except itself. Now, given an integer n, write 阅读全文

摘要： Given two strings representing two complex numbers. You need to return a string representing their multiplication. Note i2 = -1 according to the defin 阅读全文

摘要： Given an array where elements are sorted in ascending order, convert it to a height balanced BST. 思路： 由于是有序数组，那么根节点肯定是中间的那个数字，然后递归处理左子树和右子树即可。 阅读全文

摘要： Given a binary tree, find the maximum path sum. For this problem, a path is defined as any sequence of nodes from some starting node to any node in th 阅读全文

摘要： Given a string, find the length of the longest substring without repeating characters. Examples: Given "abcabcbb", the answer is "abc", which the leng 阅读全文

摘要： Implement pow(x, n). 开始的时候思路很朴素，隐约觉得不太对劲。。果然，超时了。 然后，再仔细琢磨，发现可以缩短时间，缩短到 O(lgn)的复杂度。 比如8个2相乘的话，可以表示为4的平方，4又可以表示为2的平方，只需三次即可算出。 参考： https://discuss.leet 阅读全文

摘要： A message containing letters from A-Z is being encoded to numbers using the following mapping: 'A' -> 1 'B' -> 2 ... 'Z' -> 26 Given an encoded messag 阅读全文