07 2018 档案
摘要：1、二叉树的先序遍历。 节点->左孩子->右孩子 用递归很容易解决，但是会遇到内存溢出情况。用栈可以解决找个问题。 根据前序遍历访问的顺序，优先访问根结点，然后再分别访问左孩子和右孩子。即对于任一结点，其可看做是根结点，因此可以直接访问，访问完之后，若其左孩子不为空，按相同规则访问它的左子树；当访问
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摘要：Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n. Example: Input: 13 Output: 6 Exp
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摘要：1、字符串的全排列 题目：{a,b,c}要求输出{abc,acb,bac,bca,cab,cba}。 字符串全排列可以把字符串看成两个部分，第一个部分为它的一个字符，第二部分是后面的字符。 分两步完成：首先求所有可能出现在第一个位置的字符，即把第一个字符与后面的所有字符交换。第二步固定第一个字符，求
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摘要：问题：输入一个整形数组，里面又正数也有负数。数组中一个或连续多个整数组成一个子数组，求所有子数组和的最大值。 典型的动态规划思想，因为每个状态都和前一个状态紧密相关。 因为这是一个一维数组，所以我们优先考虑用一维数组dp来做。 1、维护一个dp数组，dp[i]表示以第i个位置结尾的子数组的和的最大值
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摘要：Top K问题比较常见啦，这里总结一下方法。 1、用最小堆来做。 思路是先利用数组中前k个数字建一个最小堆，然后将剩余元素与堆顶元素进行比较，如果某个元素比堆顶元素大，就替换掉堆顶元素，并且重新调整成最小堆。 到这里，堆中保存着的其实是前k个最大的数字。堆顶就是第K个最大的数字。这样前k个，第k个都
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摘要：1、将一个字符串转乘整数 例如“1234”->1234 现在研究这段代码，有什么问题呢？首先，没有判断正负号，如果输入是“-1234”，就错了；其次，没有考虑int变量的范围，如果超过Integer.maxvalue，程序就会崩溃；最后就是如果输入有特殊字符，比如输入“123#￥%34”，这个时候应
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摘要：字符串编辑距离 字符串的编辑距离，又称为Levenshtein距离，由俄罗斯的数学家Vladimir Levenshtein在1965年提出。是指利用字符操作，把字符串A转换成字符串B所需要的最少操作数。其中，字符操作包括： 删除一个字符 插入一个字符 修改一个字符 例如对于字符串"if"和"iff
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摘要：1、Reverse Linked ListⅠ Reverse a singly linked list. Example: Input: 1->2->3->4->5->NULL Output: 5->4->3->2->1->NULL Follow up: A linked list can be r
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摘要：1、判断一个迷宫是否有出口 这个题目是我自己编的，leetcode上并没有这样的题目。为了锻炼自己的DFS，这个题目应该还是比较简单的，用深搜就可以完成，和之前做的max area of island有异曲同工之妙。 poll出迷宫问题： 、 如图所示的迷宫，0代表可以走，1代表有墙。要求从左上角到
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摘要：Given a non-empty 2D array grid of 0's and 1's, an island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) Yo
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摘要：Given a directed, acyclic graph of N nodes. Find all possible paths from node 0 to node N-1, and return them in any order. The graph is given as follo
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摘要：A sequence of number is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the
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摘要：Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements. Example: Input:
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摘要：今天总结一下用Floyd算法来判断链表中是否有环，如果有环，如何找到环的入口。这一系列问题。 1、Linked List Cycle Ⅰ Given a linked list, determine if it has a cycle in it. Follow up:Can you solve i
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摘要：Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist.
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摘要：今天来总结一下Missing Number一系列问题 1、Find All Numbers Disappeared in an Array Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements
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摘要：Given an array consists of non-negative integers, your task is to count the number of triplets chosen from the array that can make triangles if we tak
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摘要：Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters. This
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摘要：Given an unsorted array of integers, find the length of longest increasing subsequence. Example: Input: [10,9,2,5,3,7,101,18] Output: 4 Explanation: T
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摘要：Given two words word1 and word2, find the minimum number of steps required to make word1 and word2 the same, where in each step you can delete one cha
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摘要：Given two strings s1, s2, find the lowest ASCII sum of deleted characters to make two strings equal. Example 1: Input: s1 = "sea", s2 = "eat" Output:
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摘要：Given a string, your task is to count how many palindromic substrings in this string. The substrings with different start indexes or end indexes are c
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摘要：You are given a string representing an attendance record for a student. The record only contains the following three characters: 'A' : Absent. 'L' : L
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摘要：Given a string and an integer k, you need to reverse the first k characters for every 2k characters counting from the start of the string. If there ar
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摘要：Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longestpath betwee
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摘要：You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you cl
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摘要：Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. Example: Given nums = [-2, 0, 3, -5, 2, -1] sumR
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摘要：House RobberⅠ You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constrai
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摘要：Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1's in their binary representation and r
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摘要：今天处理一下一系列题目：Next Greater Element系列。 Next Greater Element I You are given two arrays (without duplicates) nums1 and nums2 where nums1’s elements are su
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摘要：Given 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
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摘要：Given an integer array with even length, where different numbers in this array represent different kinds of candies. Each number means one candy of th
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摘要：Give a string s, count the number of non-empty (contiguous) substrings that have the same number of 0's and 1's, and all the 0's and all the 1's in th
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摘要：Given a sorted (in ascending order) integer array nums of n elements and a target value, write a function to search target in nums. If target exists,
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摘要：There is a brick wall in front of you. The wall is rectangular and has several rows of bricks. The bricks have the same height but different width. Yo
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摘要：Given a binary tree, return the inorder traversal of its nodes' values. Example: Input: [1,null,2,3] 1 \ 2 / 3 Output: [1,3,2] Follow up: Recursive so
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摘要：Given a positive integer, check whether it has alternating bits: namely, if two adjacent bits will always have different values. Example 1: Input: 5 O
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摘要：We are given the head node root of a binary tree, where additionally every node's value is either a 0 or a 1. Return the same tree where every subtree
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摘要：Given a list of daily temperatures, produce a list that, for each day in the input, tells you how many days you would have to wait until a warmer temp
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摘要：Given a string, sort it in decreasing order based on the frequency of characters. Example 1: Input: "tree" Output: "eert" Explanation: 'e' appears twi
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摘要：A website domain like "discuss.leetcode.com" consists of various subdomains. At the top level, we have "com", at the next level, we have "leetcode.com
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摘要：Given n points in the plane that are all pairwise distinct, a "boomerang" is a tuple of points (i, j, k) such that the distance between iand j equals
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摘要：Given two strings A and B of lowercase letters, return true if and only if we can swap two letters in A so that the result equals B. Example 1: Input:
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摘要：Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as: a binary tree in which the dep
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摘要：Given two strings S and T, return if they are equal when both are typed into empty text editors. # means a backspace character. Example 1: Input: S =
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摘要：We have two special characters. The first character can be represented by one bit 0. The second character can be represented by two bits (10 or 11). N
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摘要：使用滑动窗口法来解决substring问题的模板如下： 这里是leetcode大神给出的通用模板，针对每个题目的不同会有一些差别。但是整体的思路就是两个指针，一个map，一个counter标记（视题目而定，也可能没有）。具体的思路就是先滑动窗口，找到一个窗口内包含一个结果；然后缩小窗口，判断结果。
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摘要：Valid Anagram Given two strings s and t , write a function to determine if t is an anagram of s. Example 1: Input: s = "anagram", t = "nagaram" Output
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摘要：In a forest, each rabbit has some color. Some subset of rabbits (possibly all of them) tell you how many other rabbits have the same color as them. Th
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摘要：Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree [1,2,2,3,4,4,3] is symmet
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摘要：There are n bulbs that are initially off. You first turn on all the bulbs. Then, you turn off every second bulb. On the third round, you toggle every
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