Given two words (start and end), and a dictionary, find all shortest transformation sequence(s) from start to end, such that: Only one letter can be changed at a time Each intermediate word must exist in the dictionary For example, Given:start = "hit…

Given a string s, partition s such that every substring of the partition is a palindrome. Return the minimum cuts needed for a palindrome partitioning of s. For example, given s = "aab",Return 1 since the palindrome partitioning ["aa",…

Given an array of integers, every element appears three times except for one. Find that single one. Note:Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? 题解:线性时间,O(1)的空间复杂度,只能把整数写成二进制的形式运算了.具体…

Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums toT. Each number in C may only be used once in the combination. Note: All numbers (including target) will be posit…

Given an array of non-negative integers, you are initially positioned at the first index of the array. Each element in the array represents your maximum jump length at that position. Your goal is to reach the last index in the minimum number of jumps…

Follow up for "Unique Paths": Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space is marked as 1 and 0 respectively in the grid. For example, There is one obstacle in the middl…

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example,Given n = 3, You should return the following matrix: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ] 题解:以前做过的Spiral Matrix是给一个矩阵螺旋式的输出,这道题是给一个n,螺旋式的…

package y2019.Algorithm.array; import java.util.ArrayList; import java.util.List; /** * @ProjectName: cutter-point * @Package: y2019.Algorithm.array * @ClassName: GetRow * @Author: xiaof * @Description: 119. Pascal's Triangle II * Given a non-negativ…

主要用于记录在LeetCode刷题的过程中学习到的一些思想和自己的想法,希望通过leetcode提升自己的编程素养 :p 高效leetcode刷题小诀窍(这只是目前对我自己而言的小方法,之后会根据自己的切身经历更新): 算法不是纯粹拼智商的,智商高,就一定很厉害,不够聪明,就一定不行.算法是一种技能,是可以通过科学合理的方式训练出来的能力.目前国内大厂的算法考察,基本不会超过leetcode 中等难度,上限难度基本都是leetcode 中等题里面的中等难度 基本的算法数据结构是有限的.比如说链表…

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? 题解:简单的模拟题,每次用answer列表存放上一层的值,用temp列表存放当前层的值,只要计算好temp中需要重新计算的元素的索引范围[1,i-1]…

问题 该文章的最新版本已迁移至个人博客[比特飞],单击链接 https://www.byteflying.com/archives/3690 访问. 给定一个非负索引 k,其中 k ≤ 33,返回杨辉三角的第 k 行. 在杨辉三角中,每个数是它左上方和右上方的数的和. 输入: 3 输出: [1,3,3,1] 你可以优化你的算法到 O(k) 空间复杂度吗? Given a non-negative index k where k ≤ 33, return the kth index row of…

题目 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? 分析 与上题LeetCode 118 Pascal's Triangle本质相同: 需要注意的是,本题参数 k = 3 代表下标为3的那行元…

学好算法很重要,然后要学好算法,大量的练习是必不可少的,LeetCode是我经常去的一个刷题网站,上面的题目非常详细,各个标签的题目都有,可以整体练习,本公众号后续会带大家做一做上面的算法题. 官方链接:https://leetcode-cn.com/problemset/all/ 一.题意 难度:中等 https://leetcode-cn.com/problems/integer-to-roman/ 罗马数字包含以下七种字符:I, V, X, L,C,D 和 M. 字符 数值 I 1 V 5…

本人算法还是比较菜的,因此大部分在刷基础题,高手勿喷 选择Python进行刷题,因为坑少,所以不太想用CPP: 1.买股票的最佳时期2 给定一个数组,它的第 i 个元素是一支给定股票第 i 天的价格. 设计一个算法来计算你所能获取的最大利润.你可以尽可能地完成更多的交易(多次买卖一支股票). 注意:你不能同时参与多笔交易(你必须在再次购买前出售掉之前的股票). 思路:买高不买低,向上即可 class Solution(object): def maxProfit(self, prices): "…

1.何为双指针 双指针主要用来遍历数组,两个指针指向不同的元素,从而协同完成任务.我们也可以类比这个概念,推广到多个数组的多个指针. 若两个指针指向同一数组,遍历方向相同且不会相交,可以称之为滑动窗口(两个指针包围的区域为当前的窗口),经常用于区间搜索. 若两个指针指向同一数组,但是遍历方向相反,那我们可以用来进行搜索,这时我们要搜索的数组往往需要排序好. 2.双指针类型 在目前的刷到过的题目种,遇到了两类双指针问题 第一类是快慢指针,顾名思义,就是一个fast指针,一个slow指针,一前一后,…

Description Given a non-negative index k where k ≤ 33, return the kth index row of the Pascal's triangle. Note that the row index starts from 0. In Pascal's triangle, each number is the sum of the two numbers directly above it. Example: Input: Output…

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below. For example, given the following triangle [ [2], [3,4], [6,5,7], [4,1,8,3] ]  The minimum path sum from top to bottom is 11 (…

Say you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy one and sell one share of the stock multiple times). Ho…

What if the given tree could be any binary tree? Would your previous solution still work? Note: You may only use constant extra space. For example,Given the following binary tree, 1 / \ 2 3 / \ \ 4 5 7 After calling your function, the tree should loo…

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. For example,Given 1->2->3->3->4->4->5, return 1->2->5.Given 1->1->1->2->3, return 2->3.…

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]. 题解:跟Permutation差不多,只是这次会有重复的元素,如下图所示,如果只用DFS的话就会产生重复的排列: 上…

Given n, generate all structurally unique BST's (binary search trees) that store values 1...n. For example,Given n = 3, your program should return all 5 unique BST's shown below. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ \ 2 1 2 3 题解:递归的枚举1~n的每个节点为根节点,…

Given a collection of integers that might contain duplicates, S, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example,If S = [1,2,2], a solution is:…

Follow up for "Search in Rotated Sorted Array":What if duplicates are allowed? Would this affect the run-time complexity? How and why? Write a function to determine if a given target is in the array. 题解:如果没有重复的元素,那么就可以根据target是否在某一半而扔掉另外一半.但是如果有…

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? 判断一个链表是否有环. 题解: 设置两个指针p1和p2: p1每次走一步,p2每次走两步,如果在这个过程中,p2为空,则没有环:否则两个指针必然相遇,则有环: 接下来找环的起点,将p1挪动到链表起始,…

Follow up for N-Queens problem. Now, instead outputting board configurations, return the total number of distinct solutions. 题解:参见http://www.cnblogs.com/sunshineatnoon/p/3853170.html 只要求求出解的个数,稍微改一下代码就可以了:用私有变量result记录解的数目,当搜索到一个解的时候,result+1即可. 代码如下…

Follow up for "Remove Duplicates":What if duplicates are allowed at most twice? For example,Given sorted array A = [1,1,1,2,2,3], Your function should return length = 5, and A is now [1,1,2,2,3]. 题解: 设置两个变量:右边kepler和前向游标forward.如果当前kepeler所指的元素和…

Reverse a linked list from position m to n. Do it in-place and in one-pass. For example:Given 1->2->3->4->5->NULL, m = 2 and n = 4, return 1->4->3->2->5->NULL. Note:Given m, n satisfy the following condition:1 ≤ m ≤ n ≤ lengt…

Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root). For example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7 return its bottom-up level order tr…

(1)Best Time to Buy and Sell Stock Total Accepted: 10430 Total Submissions: 33800My Submissions Say you have an array for which the ith element is the price of a given stock on day i. If you were only permitted to complete at most one transaction (ie…