ljffdream的专栏

【题目】A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).The robot can only move either down or right at any point in time. The robot is trying to

【题目】Given a list of non negative integers, arrange them such that they form the largest number.For example, given [3, 30, 34, 5, 9], the largest formed number is9534330.Note: The result may

【题目】Given aninteger n,generate a square matrix filled with elements from 1 to n2 inspiral order.For example,Given n = 3,Youshould return the following matrix:[  [ 1, 2, 3 ],  [ 8, 9, 4 ]

【题目】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

【题目】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.You

【题目】Given a collection ofintervals, merge all overlapping intervals.For example,Given [1,3],[2,6],[8,10],[15,18],return [1,6],[8,10],[15,18].【思路】思路就是，先对进来的这一个list 的inteval进行比较，排序，排序的时候

[timu]Given a 2D board and a word, find if the word exists in the grid.The word can be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horizontal

【题目】Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.Note: You can only move either down

【题目】Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area.【思路】只能说不明觉厉：The DP solution proceeds row by row, starting f

[timu]Follow up for "Remove Duplicates":What if duplicates are allowed at most twice?For example,Given sorted array nums = [1,1,1,2,2,3],Your function should return length = 5, with

【题目】【思路】My idea is simple: store states of each row in the first of that row, and store states of each column in the first of that column. Because the state of row0 and the state of column0

[timu]Search a 2D MatrixTotal Accepted: 52191 Total Submissions: 164580Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the followin

【题目】Largest Rectangle in Histogram Total Accepted: 42804 Total Submissions: 188970My SubmissionsQuestion Solution Given n non-negative integers representing the histogram

【题目】Given a collection of integers thatmight contain duplicates, nums,return all possible subsets.Note:Elements in a subset must be in non-descending order.The solution set must not contai

【题目】Given preorder and inorder traversal of a tree, construct the binary tree.【思路】Hint:A good way to attempt this question is to work backwards. Approach this question by drawing a binary

【题目】Given inorder and postorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.【思路】pretty similar with that

【题目】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], [

[timu] Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adja

【题目】 Given n non-negative integers representing anelevation map where the width of each bar is 1, compute how much water it isable to trap after raining.For example, Given [0,1,0,2,1,0,1,3,2,1

【题目】You are given an n x n 2D matrix representing an image.Rotate the image by 90 degrees (clockwise).【思路】The idea was firstly transpose the matrix and then flip it symmetrically.

【题目】Given an unsortedinteger 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 us

【题目】Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.You may assume no duplicates in th

【题目】Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue.Here, we will use the

【题目】Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.You may assume that the array is non-empty and the majorit

【题目】A peak element is an element that is greater than its neighbors.Given an input array where num[i] ≠ num[i+1], find a peak element and return its index.The array may contain multipl

【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

[题目]Implement a basic calculator to evaluate a simple expression string.The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers an

【题目】Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every el

【题目】Given a sorted integer array without duplicates, return the summary of its ranges.For example, given [0,1,2,4,5,7], return ["0->2","4->5","7"].Credits:Special thanks to @jianchao.l

[题目]There are two sorted arrays nums1 and nums2 of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).[分析][code

[题目] medianFollow 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 tar

【题目】Suppose a sorted array is rotated at some pivot unknown to you beforehand.(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).Find the minimum element.You may assume no duplicate

【题目】Rotate an array of n elements to the right by k steps.For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].Note:Try to come up as many solut

【题目】Given a set of distinct integers, nums, return all possible subsets.Note:Elements in a subset must be in non-descending order.The solution set must not contain duplicate subsets.

【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 parti

【题目】【思路】The problem can be simply broken down as two binary searches for the begining and end of the range, respectively:First let's find the left boundary of the range. We ini

【题目】【分析】首先，先sort,如果target > 0:【代码】using recursive 这恐怕的 O(n2)...过程：before recursion : [2]before recursion : [2, 2]before recursion : [2, 2, 2]after recursion and remove :

【题目】Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.【思路】中心检测