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101. Symmetric Tree (easy) 判断树是否为左右对称 Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this 阅读全文
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1. Two Sum (easy) 找到数组中和为target的两个数，返回索引 2. Add Two Numbers (medium) You are given two non-empty linked lists representing two non-negative integers. 阅读全文
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1. 乘法表 题目描述 度度熊和爷爷在玩一个乘法表游戏。乘法表的第i行第j列位置的元素为i*j，并且乘法表下标编号从1开始，比如2 × 3乘法表为 1 2 3 2 4 6 爷爷十分聪明，对于n*m的乘法表，只要度度熊给出一个数k，爷爷就能立刻告诉度度熊乘法表中元素按照不减顺序排列之后，第k个元素是多 阅读全文
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1. Two Sum (easy) 找到数组中和为target的两个数，返回索引 3. Longest Substr Without Repeating Characters (medium) 最长的无重复的子字符串 18. 4Sum (medium) 找到所有和为target的四元数组 30. S 阅读全文
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3. Longest Substring Without Repeating Characters (medium) 最长的无重复的子字符串 Given a string, find the length of the longest substring without repeating char 阅读全文
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10. Regular Expression Matching (hard) # 正则表达式匹配：.和* Implement regular expression matching with support for '.' and '*'. '.' Matches any single charac 阅读全文
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1. Two Sum (easy) 找到数组中和为target的两个数，返回索引 Given an array of integers, return indices of the two numbers such that they add up to a specific target. You 阅读全文
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leetcode 笔记 Linked List 2. Add Two Numbers (medium) You are given two non-empty linked lists representing two non-negative integers. The digits are st 阅读全文