题目如下: 解题思路:既然是要求回文字符串,那么最终的输出结果就是对称的.要变成对称字符串,只要把处于对称位置上对应的两个字符中较大的那个变成较小的那个即可,假设n=1234,1和4对称所以把4变成1,2和3对称把3变成2,得到1221,看起来好像没问题了.可是如果n=1283,按照这个方法得到的结果是1221,而预期的结果应该是1331,所以需要考虑到进位和退位的问题.这就有点复杂了,简单点的方法也有,就是把进位和退位的所有情况都列举出来再做比较,得出差值最小的那个.例如n=1283,按照对称…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 题目地址: https://leetcode.com/problems/find-k-closest-elements/description/ 题目描述: Given a sorted array, two integers k and x, find the k closest elements to x in the array. The result should also b…

题目等级:Easy 题目描述: Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward. Example 1: Input: 121 Output: true Example 2: Input: -121 Output: false Explanation: From left to right, it reads -12…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 日期 题目地址:https://leetcode.com/problems/maximize-distance-to-closest-person/description/ 题目描述 In a row of seats, 1 represents a person sitting in that seat, and 0 represents that…

[LeetCode Weekly Contest 29][2017/04/23] 第17周 Binary Tree Tilt (3) Array Partition I (6) Longest Line of Consecutive One in Matrix (8) Find the Closest Palindrome (10) 第一题: 563. Binary Tree Tilt [easy] 别人写几行,我写的非常啰嗦==.树后序遍历.代码是重写过的. Given a binary tr…

[LeetCode]895. Maximum Frequency Stack 解题报告(Python) 作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 题目地址:https://leetcode.com/problems/maximum-frequency-stack/description/ 题目描述: Implement FreqStack, a class which simulates the operation of a…

[题目] Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target. Note: Elements in a quadruplet (a,b,c,d) must be in non-descending o…

[LeetCode]Minimum Depth of Binary Tree Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. 递归和非递归,此提比较简单.广度优先遍历即可.关键之处就在于如何保持访问深度. 下面是4种代码: im…

Given an index k, return the kth row of the Pascal's triangle. For example, given k = 3, Return [1,3,3,1]. Note: Could you optimize your algorithm to use only O(k) extra space? 思路:最简单的方法就是依照[Leetcode]Pascal's Triangle 的方式自顶向下依次求解,但会造成空间的浪费.若仅仅用一个vect…

53. Maximum Subarray[leetcode] Find the contiguous subarray within an array (containing at least one number) which has the largest sum. For example, given the array [-2,1,-3,4,-1,2,1,-5,4],the contiguous subarray [4,-1,2,1] has the largest sum = 6. 挑…

27. Remove Element[leetcode] Given an array and a value, remove all instances of that value in place and return the new length. Do not allocate extra space for another array, you must do this in place with constant memory. The order of elements can b…

[刷题][LeetCode]总 用动画的形式呈现解LeetCode题目的思路 参考链接-空 007-整数反转 方法: 弹出和推入数字 & 溢出前进行检查 思路: 我们可以一次构建反转整数的一位数字.在这样做的时候,我们可以预先检查向原整数附加另一位数字是否会导致溢出. 算法: 反转整数的方法可以与反转字符串进行类比. 我们想重复"弹出" x 的最后一位数字,并将它"推入"到 rev 的后面.最后,rev 将与 x 相反. 要在没有辅助堆栈 / 数组的帮助下…

[刷题][LeetCode]总 用动画的形式呈现解LeetCode题目的思路 参考链接 000-十大经典排序算法…

Algorithm [leetcode]893. Groups of Special-Equivalent Strings https://leetcode.com/problems/groups-of-special-equivalent-strings/ 1)problem You are given an array A of strings. Two strings S and T are special-equivalent if after any number of moves,…

Algorithm [leetcode]657. Robot Return to Origin https://leetcode.com/problems/robot-return-to-origin/ 1)problem There is a robot starting at position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robot ends up at (0,…

Algorithm [leetcode]557. Reverse Words in a String III https://leetcode.com/problems/reverse-words-in-a-string-iii/ 1)problem Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace…

写在前面   老粉丝可能知道现阶段的LeetCode刷题将按照某一个特定的专题进行,之前的[贪心算法]已经结束,虽然只有三个题却包含了简单,中等,困难这三个维度,今天介绍的是第二个专题[数组] 数组(Array)是一种线性表数据结构.它用一组连续的内存空间,来存储一组具有相同类型的数据.在每一种编程语言中,基本都会有数组这种数据类型.不过,它不仅仅是一种编程语言中的数据类型,还是一种最基础的数据结构. 贪心算法回顾: [LeetCode]贪心算法--买卖股票的最佳时机II(122) [LeetC…

全排列问题.经常使用的排列生成算法有序数法.字典序法.换位法(Johnson(Johnson-Trotter).轮转法以及Shift cursor cursor* (Gao & Wang)法. [题目] Given a collection of numbers, return all possible permutations. For example, [1,2,3] have the following permutations: [1,2,3], [1,3,2], [2,1,3], [2…

[题目] Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example, [1,1,2] have the following unique permutations: [1,1,2], [1,2,1], and [2,1,1]. [解析] 题意:求一个数组的全排列.与[LeetCode]Permutations 解题报告 不同的是…

[leetcode]438. Find All Anagrams in a String Given a string s and a non-empty string p, find all the start indices of p's anagrams in s. Strings consists of lowercase English letters only and the length of both strings s and p will not be larger than…

[LeetCode]First Missing Positive Given an unsorted integer array, find the first missing positive integer. For example, Given [1,2,0] return 3, and [3,4,-1,1] return 2. Your algorithm should run in O(n) time and uses constant space. 找到第一个没有出现的正整数 思路:…

Given a linked list, return the node where the cycle begins. If there is no cycle, return null. Follow up: Can you solve it without using extra space? 思路:由[Leetcode]Linked List Cycle可知.利用一快一慢两个指针可以推断出链表是否存在环路. 如果两个指针相遇之前slow走了s步,则fast走了2s步.而且fast已经在长…

使用最小花费爬楼梯 数组的每个索引做为一个阶梯,第 i个阶梯对应着一个非负数的体力花费值 cost[i](索引从0开始). 每当你爬上一个阶梯你都要花费对应的体力花费值,然后你可以选择继续爬一个阶梯或者爬两个阶梯. 您需要找到达到楼层顶部的最低花费.在开始时,你可以选择从索引为 0 或 1 的元素作为初始阶梯. 示例 1: 输入: cost = [10, 15, 20] 输出: 15 解释: 最低花费是从cost[1]开始,然后走两步即可到阶梯顶,一共花费15. 示例 2: 输入: cost =…

题目如下: An integer has sequential digits if and only if each digit in the number is one more than the previous digit. Return a sorted list of all the integers in the range [low, high] inclusive that have sequential digits. Example 1: Input: low = 100,…

题目等级:4Sum II(Medium) 题目描述: Given four lists A, B, C, D of integer values, compute how many tuples (i, j, k, l) there are such that A[i] + B[j] + C[k] + D[l] is zero. To make problem a bit easier, all A, B, C, D have same length of N where 0 ≤ N ≤ 500…

题目等级:4Sum(Medium) 题目描述: Given an array nums of n integers and an integer target, are there elements a, b, c, and d in nums such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target. Note: The solution se…

题目等级:3Sum(Medium) 题目描述: Given an array nums of n integers, are there elements a, b, c in nums 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. Exam…

Best Time to Buy and Sell Stock with Transaction Fee 题目等级:Medium 题目描述: Your are given an array of integers prices, for which the i-th element is the price of a given stock on day i; and a non-negative integer fee representing a transaction fee. You m…

题目如下: 解题思路:本题是[leetcode]473. Matchsticks to Square的姊妹篇,唯一的区别是[leetcode]473. Matchsticks to Square指定了分成四个子数组,而本题分成的份数不定,作为参数输入.另外,本题的测试用例好像复杂一点,因此我过滤掉了nums中值等于avg的元素,不参与后面的DFS计算,提高效率. 代码如下: class Solution(object): def canPartitionKSubsets(self, nums,…

题目如下: Given an array of scores that are non-negative integers. Player 1 picks one of the numbers from either end of the array followed by the player 2 and then player 1 and so on. Each time a player picks a number, that number will not be available f…