地山谦的博客

1.题目输入一个链表的头节点，从尾到头反过来返回每个节点的值（用数组返回）。示例 1：输入：head = [1,3,2]输出：[2,3,1]2. 思路2.1递归递推阶段： 每次传入 head.next ，以 head == null（即走过链表尾部节点）为递归终止条件，此时直接返回。回溯阶段：层层回溯时，将当前节点值加入列表，即tmp.add(head.val)。最终，将列表 ...

一、题目请实现一个函数，把字符串 s 中的每个空格替换成"%20"。示例 1：输入：s = “We are happy.”输出：“We%20are%20happy.”二、思路2.1 遍历用另外一个初始为空的字符串来存储结果，遍历一遍字符串，每遇到非空格就直接在末尾加上该字符，如果为空则替换加到末尾。2.2 StringBuilder的使用StringBuilder是可变类，线性...

1. 题目在一个 n * m 的二维数组中，每一行都按照从左到右递增的顺序排序，每一列都按照从上到下递增的顺序排序。请完成一个函数，输入这样的一个二维数组和一个整数，判断数组中是否含有该整数。2. 示例示例:现有矩阵 matrix 如下：[[1, 4, 7, 11, 15],[2, 5, 8, 12, 19],[3, 6, 9, 16, 22],[10, 13,...

1. 题目在一个长度为 n 的数组 nums 里的所有数字都在 0～n-1 的范围内。数组中某些数字是重复的，但不知道有几个数字重复了，也不知道每个数字重复了几次。请找出数组中任意一个重复的数字。2.示例示例 1：输入：[2, 3, 1, 0, 2, 5, 3]输出：2 或 3限制：2 <= n <= 1000003. 思路遍历该数组，每遇到一个数字查询是否在哈希表...

1. problem descriptionYou 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 t...

1. problem descriptionThere 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)).You m...

1. problem descriptionGiven 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)...

1. problem descriptionGiven 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 solut...

1. problem descriptionGiven an array nums of n integers and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume...

problem descriptionGiven a string containing just the characters ‘(’, ‘)’, ‘{’, ‘}’, ‘[’ and ‘]’, determine if the input string is valid.An input string is valid if:Open brackets must be closed by...

1. problem descriptionMerge 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.将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个...

1. problem descriptionMerge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.合并 k 个排序链表，返回合并后的排序链表。请分析和描述算法的复杂度。Input:[1->4->5,1->3->4,2-...

1. problem descriptionGiven a sorted array nums, remove the duplicates in-place such that each element appear only once and return the new length.Do not allocate extra space for another array, you m...

1. problem descriptionSuppose an array sorted in ascending order 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]).You are given a target value...

1. problem descriptionGiven an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.Example:Input: [-2,1,-3,4,-1,2,1,-5,4]...

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.Example 1:Input:[[ 1, 2, 3 ],[ 4, 5, 6 ],[ 7, 8, 9 ]]Output: [1,2,3,6,9,8,7,4,5]Examp...

1. problem descriptionGiven a positive integer n, generate a square matrix filled with elements from 1 to n^2 in spiral order.Example:Input: 3Output:[[ 1, 2, 3 ],[ 8, 9, 4 ],[ 7, 6, 5 ]]2. s...

1. problem descriptionGiven a linked list, rotate the list to the right by k places, where k is non-negative.给定一个链表，旋转链表，将链表每个节点向右移动 k 个位置，其中 k 是非负数。Example 1:Input: 1->2->3->4->5-&gt...

1. problem descriptionA 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 ...

1. problem descriptionGiven a set of distinct integers, nums, return all possible subsets (the power set).给定一组不含重复元素的整数数组 nums，返回该数组所有可能的子集（幂集）。Note: The solution set must not contain duplicate sub...

1. problem descriptionGiven two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.Note:The number of elements initialized in nums1 and nums2 are m and n respectivel...

1. problem descriptionGiven a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.Note: A leaf is a...

1. problem descriptionSay you have an array for which the i^th 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...

1. problem descriptionGiven a non-empty binary tree, find the maximum path sum.For this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along the ...

1. problem descriptionGiven a non-empty array of integers, every element appears twice except for one. Find that single one.给定一个非空整数数组，除了某个元素只出现一次以外，其余每个元素均出现两次。Note:Your algorithm should have a l...

1. problem descriptionDesign and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and put.get(key) ：Get the value (will always be posi...

1. problem descriptionSort a linked list in O(n log n) time using constant space complexity（在 O(n log n) 时间复杂度和常数级空间复杂度下）.eg1:Input: 4->2->1->3Output: 1->2->3->4eg2:Input: -...

1. problem descriptionDesign a stack that supports push, pop, top, and retrieving the minimum element in constant time.设计一个支持 push，pop，top 操作，并能在常数时间内检索到最小元素的栈。push(x) – Push element x onto stack....

1. problem descriptionGiven 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...

problem descriptionFind the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.Example 1:Input: [3,2,1,5,6,4] and k...

1. problem descriptionGiven 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 fa...

1. problem descriptionGiven a binary search tree, write a function kthSmallestto find the kth smallest element in it.Note:You may assume k is always valid, 1 ≤ k ≤ BST’s total elements.（你可以假设 k 总是有...

1. problem descriptionGiven an integer, write a function to determine if it is a power of two.Example 1:Input: 1Output: trueExplanation: 2^0 = 1Example 2:Input: 16Output: trueExplanation: ...

1. problem descriptionGiven a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.According to the definition of LCA on Wikipedia: “The lowest common ancest...

1. problem descriptionGiven a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.According to the definition of LCA on Wikipedia: “The lowest common ancestor is define...

目录1. problem description2. solution1. problem descriptionGiven an array nums of n integers where n > 1, return an array output such that output[i] is equal to the product of all the elements of ...

1. problem descriptionYou are playing the following Nim Game with your friend: There is a heap of stones on the table, each time one of you take turns to remove 1 to 3 stones. The one who removes the...