637 Average of Levels in Binary Tree
摘要：
Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array. Example 1: 阅读全文
posted @ 2018-08-09 17:40 猪猪🐷 阅读(94) 评论(0) 推荐(0)
102 Binary Tree Level Order Traversal
摘要：
Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level). For example:Given binary tree [3 阅读全文
posted @ 2018-08-09 17:39 猪猪🐷 阅读(169) 评论(0) 推荐(0)
Buy and Sell Stock series
摘要：
121. Best Time to Buy and Sell Stock Say you have an array for which the ith element is the price of a given stock on day i. If you were only permitte 阅读全文
posted @ 2018-08-09 17:39 猪猪🐷 阅读(159) 评论(0) 推荐(0)
49 Group Anagrams
摘要：
Given an array of strings, group anagrams together. Example: Input: ["eat", "tea", "tan", "ate", "nat", "bat"], Output: [ ["ate","eat","tea"], ["nat", 阅读全文
posted @ 2018-08-09 17:38 猪猪🐷 阅读(128) 评论(0) 推荐(0)
680 Valid Palindrome II
摘要：
Given a non-empty string s, you may delete at most one character. Judge whether you can make it a palindrome. Example 1: Example 2: 阅读全文
posted @ 2018-08-09 17:35 猪猪🐷 阅读(109) 评论(0) 推荐(0)
23. Merge k Sorted Lists
摘要：
Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. Example: 阅读全文
posted @ 2018-08-09 17:34 猪猪🐷 阅读(93) 评论(0) 推荐(0)
235. Lowest Common Ancestor of a Binary Search Tree
摘要：
带返回值的 recursion Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST. According to the definition of 阅读全文
posted @ 2018-08-09 17:34 猪猪🐷 阅读(93) 评论(0) 推荐(0)
286. Walls and Gates
摘要：
You are given a m x n 2D grid initialized with these three possible values. Fill each empty room with the distance to its nearest gate. If it is impos 阅读全文
posted @ 2018-08-09 17:33 猪猪🐷 阅读(119) 评论(0) 推荐(0)
242. Valid Anagram
摘要：
Given two strings s and t , write a function to determine if t is an anagram of s. Example 1: Example 2: Note:You may assume the string contains only 阅读全文
posted @ 2018-08-09 17:32 猪猪🐷 阅读(82) 评论(0) 推荐(0)
125. Valid Palindrome
摘要：
Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. Note: For the purpose of this problem, w 阅读全文
posted @ 2018-08-09 17:31 猪猪🐷 阅读(94) 评论(0) 推荐(0)
387. First Unique Character in a String
摘要：
Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1. Examples: 阅读全文
posted @ 2018-08-09 17:30 猪猪🐷 阅读(82) 评论(0) 推荐(0)
438. Find All Anagrams in a String (find all the start indices of p's anagrams in s.)
摘要：
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 阅读全文
posted @ 2018-08-09 17:29 猪猪🐷 阅读(125) 评论(0) 推荐(0)
212. Word Search II
摘要：
再尝试用 isWord boolean 的方式创建 trienode , 做下这道题。 Given a 2D board and a list of words from the dictionary, find all words in the board. Each word must be c 阅读全文
posted @ 2018-08-09 17:28 猪猪🐷 阅读(136) 评论(0) 推荐(0)
76 - Minimum Window Substring
摘要：
Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n). Example: Note: If there i 阅读全文
posted @ 2018-08-09 17:28 猪猪🐷 阅读(150) 评论(0) 推荐(0)
208 implement trie
摘要：
208 impement trie Implement a trie with insert, search, and startsWith methods. Example: Trie trie = new Trie(); trie.insert("apple"); trie.search("apple"); // returns true trie.search("app"); ... 阅读全文
posted @ 2018-08-09 17:27 猪猪🐷 阅读(216) 评论(0) 推荐(0)
Sparse vector multiplication
摘要：
// sparse vector mul // 1. the the vector is sparse , how to save time // only save the non zero element // what data strucure do you want to use to keep the non zero element // use list of list... 阅读全文
posted @ 2018-08-09 17:26 猪猪🐷 阅读(193) 评论(0) 推荐(0)
234. Palindrome Linked List
摘要：
234. Palindrome Linked List Could you do it in O(n) time and O(1) space? O(1) space means no extra space, no extra data structure https://leetcode.com 阅读全文
posted @ 2018-08-09 17:23 猪猪🐷 阅读(85) 评论(0) 推荐(0)
32. Longest Valid Parentheses
摘要：
Longest Valid Parentheses https://www.youtube.com/watch?v=M1Vw5Tk1rw4 阅读全文
posted @ 2018-08-09 17:23 猪猪🐷 阅读(99) 评论(0) 推荐(0)
75 - Sort Colors
摘要：
75 - Sort Colors https://www.youtube.com/watch?v=yTwW8WiGrKw 75, sort colors, rainbow sort .. sort k colors Given an array with n objects colored red, 阅读全文
posted @ 2018-08-09 17:22 猪猪🐷 阅读(138) 评论(0) 推荐(0)
29. Divide Two Integers
摘要：
Given two integers dividend and divisor, divide two integers without using multiplication, division and mod operator. Return the quotient after dividing dividend by divisor. The integer division sh... 阅读全文
posted @ 2018-08-09 17:21 猪猪🐷 阅读(107) 评论(0) 推荐(0)
给俩排好序的数组，找出两个数组的最小差
摘要：
给俩排好序的数组，找出两个数组的最小差，比如 [3 5 7] [5 9 12], 我这个代码对吗？ public int minDifference(int[] a, int[] b){ int i = 0; int j = 0; int result = Math.abs(a[i] - b[j]); while( i b[j]){ result ... 阅读全文
posted @ 2018-08-09 17:17 猪猪🐷 阅读(199) 评论(0) 推荐(0)
80. Remove Duplicates from Sorted Array II
摘要：
Given a sorted array nums, remove the duplicates in-place such that duplicates appeared at most twice and return the new length. Do not allocate extra 阅读全文
posted @ 2018-08-09 17:13 猪猪🐷 阅读(76) 评论(0) 推荐(0)
110. Balanced Binary Tree
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 阅读全文
posted @ 2018-08-09 17:12 猪猪🐷 阅读(94) 评论(0) 推荐(0)
173. Binary Search Tree Iterator
摘要：
Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST. Calling next() will return the n 阅读全文
posted @ 2018-08-09 17:11 猪猪🐷 阅读(85) 评论(0) 推荐(0)
333. Largest BST Subtree
摘要：
333. Largest BST Subtree I feel this is post order traversal https://www.youtube.com/watch?v=4fiDs7CCxkc https://leetcode.com/problems/largest-bst-sub 阅读全文
posted @ 2018-08-09 17:11 猪猪🐷 阅读(138) 评论(0) 推荐(0)
98. Validate Binary Search Tree
摘要：
带返回值的 recursion. time： O(N), N is the number of nodes in the bst, space is O(1) , no extra space is used Given a binary tree, determine if it is a val 阅读全文
posted @ 2018-08-09 17:09 猪猪🐷 阅读(103) 评论(0) 推荐(0)
572. Subtree of Another Tree
摘要：
Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a 阅读全文
posted @ 2018-08-09 17:06 猪猪🐷 阅读(92) 评论(0) 推荐(0)
114. Flatten Binary Tree to Linked List
摘要：
Given a binary tree, flatten it to a linked list in-place. For example, given the following tree: The flattened tree should look like: 阅读全文
posted @ 2018-08-09 17:04 猪猪🐷 阅读(89) 评论(0) 推荐(0)
253. Meeting Rooms II
摘要：
if the new interval's start is later than the smallest end index in our pq. then we can use the same room, and update the end , put it back to the pq. 阅读全文
posted @ 2018-08-09 17:03 猪猪🐷 阅读(129) 评论(0) 推荐(0)
117. Populating Next Right Pointers in Each Node II
摘要：
Given a binary tree Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL 阅读全文
posted @ 2018-08-09 17:02 猪猪🐷 阅读(75) 评论(0) 推荐(0)
297. Serialize and Deserialize Binary Tree
摘要：
面经是 给二叉树前序输出，恢复这个树 Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or 阅读全文
posted @ 2018-08-09 16:59 猪猪🐷 阅读(111) 评论(0) 推荐(0)
116. Populating Next Right Pointers in Each Node
摘要：
Given a binary tree Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL 阅读全文
posted @ 2018-08-09 16:56 猪猪🐷 阅读(92) 评论(0) 推荐(0)
513. Find Bottom Left Tree Value
摘要：
Given a binary tree, find the leftmost value in the last row of the tree. Example 1: Example 2: 阅读全文
posted @ 2018-08-09 16:55 猪猪🐷 阅读(99) 评论(0) 推荐(0)
545. Boundary of Binary Tree
摘要：
Given a binary tree, return the values of its boundary in anti-clockwise direction starting from root. Boundary includes left boundary, leaves, and ri 阅读全文
posted @ 2018-08-09 16:54 猪猪🐷 阅读(100) 评论(0) 推荐(0)
404. Sum of Left Leaves
摘要：
Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 1 阅读全文
posted @ 2018-08-09 16:51 猪猪🐷 阅读(90) 评论(0) 推荐(0)
敬啟者給十五歲的你
摘要：
此刻正讀著這封信的你現在在哪裡 正在做些什麼事呢？ 十五歲的我 有著無法向任何人訴說的煩惱 如果是寫給未來的自己的信一定可以坦率的說出來吧 現在 我不行了 我好想哭 好想消失在世界上彷彿下一秒就要消失的我究竟該相信誰的話？ 只有一顆心 不斷的崩離破碎在痛苦之中 只能繼續不停地往前走 敬啟者：謝謝你的 阅读全文
posted @ 2018-07-24 03:03 猪猪🐷 阅读(105) 评论(0) 推荐(0)
144. Binary Tree Preorder Traversal
摘要：
Given a binary tree, return the preorder traversal of its nodes' values. Example: Input: [1,null,2,3] 1 \ 2 / 3 Output: [1,2,3] Follow up: Recursive s 阅读全文
posted @ 2018-07-19 12:41 猪猪🐷 阅读(125) 评论(0) 推荐(0)
94. Binary Tree Inorder Traversal
摘要：
Given a binary tree, return the inorder traversal of its nodes' values. Example: Follow up: Recursive solution is trivial, could you do it iteratively 阅读全文
posted @ 2018-07-19 12:23 猪猪🐷 阅读(103) 评论(0) 推荐(0)
104. Maximum Depth of Binary Tree
摘要：
Given 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 l 阅读全文
posted @ 2018-07-19 12:20 猪猪🐷 阅读(76) 评论(0) 推荐(0)
111. Minimum Depth of Binary Tree
摘要：
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 l 阅读全文
posted @ 2018-07-19 12:19 猪猪🐷 阅读(90) 评论(0) 推荐(0)
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