LeetCode 题解 序号 题目 答案 难度 1 Two Sum Java Easy 2 Add Two Numbers Java Medium 3 Longest Substring Without Repeating Characters Java Medium 4 Median of Two Sorted Arrays Java Hard 5 Longest Palindromic Substring Java Medium 6 Longest Substring Without Repeating Characters Java Medium 7 Reverse Integer Java Easy 8 String to Integer (atoi) Java Medium 9 Palindrome Number Java Easy 10 Regular Expression Matching Java Hard 11 Container With Most Water Java Medium 12 Integer to Roman Java Medium 13 Roman to Integer Java Easy 14 Longest Common Prefix Java Easy 15 3Sum Java Medium 16 3Sum Closest Java Medium 17 Letter Combinations of a Phone Number Java Medium 18 4Sum Java Medium 19 Remove Nth Node From End of List Java Medium 20 Valid Parentheses Java Medium 21 Merge Two Sorted Lists Java Medium 22 Generate Parentheses Java Medium 23 Merge k Sorted Lists Java Medium 24 Swap Nodes in Pairs Java Medium 25 Remove Duplicates from Sorted Array Java Medium 26 Maximum Subarray Java Medium 27 Best Time to Buy and Sell Stock Java Easy 28 is-subsequence Java Easy 29 min-cost-climbing-stairs Java Easy 30 remove-duplicates-from-sorted-array Java Easy