蜗牛慢慢爬 LeetCode 6. ZigZag Conversion [Difficulty: Medium]

题目 The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility) P A H N A P L S I I G Y I R And then read line by line: "PAHNAPL…

蜗牛慢慢爬 LeetCode 16. 3Sum Closest [Difficulty: Medium]

题目 Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution. For example, given array S = {-1…

蜗牛慢慢爬 LeetCode 22. Generate Parentheses [Difficulty: Medium]

题目 Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses. For example, given n = 3, a solution set is: [ "((()))", "(()())", "(())()", "()(())", "()()()" ]…

蜗牛慢慢爬 LeetCode 36.Valid Sudoku [Difficulty: Medium]

题目 Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. The Sudoku board could be partially filled, where empty cells are filled with the character '.'. A partially filled sudoku which is valid. Note: A valid Sudoku board (partia…

蜗牛慢慢爬 LeetCode 9. Palindrome Number [Difficulty: Easy]

题目 Determine whether an integer is a palindrome. Do this without extra space. Some hints: Could negative integers be palindromes? (ie, -1) If you are thinking of converting the integer to string, note the restriction of using extra space. You could a…

蜗牛慢慢爬 LeetCode 20. Valid Parentheses [Difficulty: Easy]

题目 Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]&q…

蜗牛慢慢爬 LeetCode 7. Reverse Integer [Difficulty: Easy]

题目 Reverse digits of an integer. Example1: x = 123, return 321 Example2: x = -123, return -321 Have you thought about this? Here are some good questions to ask before coding. Bonus points for you if you have already thought through this! If the integ…

蜗牛慢慢爬 LeetCode 1.Two Sum [Difficulty: Easy]

题目 Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have exactly one solution, and you may not use the same element twice. Example: Given nums = [2, 7, 11,…

蜗牛慢慢爬 LeetCode 23. Merge k Sorted Lists [Difficulty: Hard]

题目 Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. 翻译合并k个有序的链表 Hints Related Topics: LinkedList, Divide and Conquer, Heap Solution1:Divide and Conquer 参考归并排序-维基百科思路:分治,先分成两个子任务,然后递归子任务,最后回溯回来..这里就…

蜗牛慢慢爬 LeetCode 8. String to Integer (atoi) [Difficulty: Medium]

题目 Implement atoi to convert a string to an integer. Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases. Notes: It is intended for this problem to be…

蜗牛慢慢爬 LeetCode 25. Reverse Nodes in k-Group [Difficulty: Hard]

题目 Given a linked list, reverse the nodes of a linked list k at a time and return its modified list. k is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of k then left-out nodes…

# 蜗牛慢慢爬 LeetCode 21. Merge Two Sorted Lists [Difficulty: Easy]

题目 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. 翻译合并两个有序的链表 Hints Related Topics: LinkedList 参考归并排序-维基百科,可以递归也可以迭代,基本的链表操作代码 Java /** * Definition for…

蜗牛慢慢爬 LeetCode 15. 3Sum [Difficulty: Medium]

题目 Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: The solution set must not contain duplicate triplets. For example, given array S = [-…

蜗牛慢慢爬 LeetCode 10. Regular Expression Matching [Difficulty: Hard]

题目 Implement regular expression matching with support for '.' and '*'. '.' Matches any single character. '*' Matches zero or more of the preceding element. The matching should cover the entire input string (not partial). The function prototype should…

蜗牛慢慢爬 LeetCode 19. Remove Nth Node From End of List [Difficulty: Medium]

题目 Given a linked list, remove the nth node from the end of list and return its head. For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the end, the linked list becomes 1->2->3->5. Note: Giv…

蜗牛慢慢爬 LeetCode 11. Container With Most Water [Difficulty: Medium]

题目 Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a conta…

蜗牛慢慢爬 LeetCode 5.Longest Palindromic Substring [Difficulty: Medium]

题目 Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000. Example: Input: "babad" Output: "bab" Note: "aba" is also a valid answer. Example: Input: "cbbd"…

蜗牛慢慢爬 LeetCode 3. Longest Substring Without Repeating Characters [Difficulty: Medium]

题目 Given a string, find the length of the longest substring without repeating characters. Examples: Given "abcabcbb", the answer is "abc", which the length is 3. Given "bbbbb", the answer is "b", with the length of…

蜗牛慢慢爬 LeetCode 2. Add Two Numbers [Difficulty: Medium]

题目 You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list. You may assume the two numb…

LeetCode 6. ZigZag Conversion & 字符串

ZigZag Conversion 看了三遍题目才懂,都有点怀疑自己是不是够聪明... 就是排成这个样子啦,然后从左往右逐行读取返回. 这题看起来很简单,做起来,应该也很简单. 通过位置计算行数: P I N A L S I G Y A H R P I 0,0 1,1 2,2 3,3 4,2 5,1 6,0 (期望) 用简单的先思考: P A H N A P L S I I G Y I R 0,0 1,1 2,2 3,3 4,0 %4 (3+1)可以解决正常的 3,1(期望) 特殊的3(2行2排…