leetcode

面试总结 Facebook Summary

Posted by Jennifer on February 10, 2018

  • LC13 - Roman to Int: 关键在于如何判断当前该加还是减。

    ​ for1 string -> int, for 2: +=sum

  • LC15 - 3 sum 2 pointer + a while loop outside, remember to sort

  • LC17. Letter Combinations of a Phone Number: LinkedList 用来当Queue

  • LC23 Merge K sorted list - 变体 iterator

    此题先想到priorityqueue with modified comparator. Time complexity是O(nlogk)

    也可Merge sort思路 helper method merge 2 lists every time 是O(nklogn)

  • LC28 - impement strStr()

  • LC29 - Divide 2 Integers - bit manipulation

    Preprocess ： make positive

    while loop 左移divisor到头，res += «同样位数。update dividend。再循环直到dividend < divisor

  • LC31 - Next Permutation: Ex. 1322 -> 2123

  • LC33 - Search in Rotated Sorted Array: Binary Search, edge case

  • LC43 - 右往左 第i位x第j位 res 存在第i+j和i+j+1位

  • LC46,47 -Permutation - Backtrack

  • LC49 - Group Anagrams: 先sort 再hashmap查找；prime number

  • LC56 - Merge Intervals - 分别sort先

  • LC65 - Valid Number - Set booleans up front and run through by for loop with list of if statements

  • LC67 - Add Binary

  • LC71 - Simplify path Stack + HashSet

  • LC75 - Sort Colors - 2 Pointers 大约只需4line code但很容易出错 *

  • LC76 - Min Window Substring - Substring类题 注意细节

  • LC91 - Decode ways DP

  • LC93 - Restore IP Address - 3 nested for loop

  • LC98 - Tree Question https://leetcode.com/problems/validate-binary-search-tree/discuss/

  • LC102 - Binary Tree Level Order Traversal - DFS or Queue

  • LC106 Construct Binary Tree from Inorder and Postorder Travesal

  • LC114 - Flatten Binary Tree to LinkedList

  • LC125 - Two Pointer

  • LC133 - Clone Graph HashMap 存 label -> node

  • LC138 - Copy List with Random Pointer - 易有小错

  • LC139,140 Word Break DP DFS with a hashmap (s -> linkedlist)

    ​ return that linkedlist

  • LC146 LRU Cache - DLinkedListNode

  • LC158 - Read 4K Outside of loop create a char[] a

  • LC173 - Binary Search Tree Iterator Nothing Tricky, use stack + left traversal

  • LC189 - Rotate Array remember to convert k to a pivot index

  • LC191 - Number of 1 Bits - Bit Manipulation

    • 和»的区别是unsign和sign，然后 if的condition是n!=0而不是n>0

  • LC200 - Number of Islands - BFS

  • LC202 - Happy Number

  • LC203 - Remove LinkedList Elements

  • LC211 Add and Search Word - Data Structure Tree with Node[26] child

  • LC227 Basic Calculator II For loop + stack pop in */

  • LC230 - Kth Smallest Element in a BST - Tree Iterator, Binary Search

  • LC 252, 253 Meeting Rooms 253 Meeting rooms II priorityQueue to sort all intervals and then for loop to add

  • LC257 Binary Tree Paths

  • LC266 Palindrome Permutation - HashSet add then remove

  • LC273 - Integer to English Words

    • 0-9; 10- 19; 20-90
    • helper() check below 10,20,100,1000,1000000,1000000000 and call helper recursively

  • LC277 - Find Celebrity 2 Pass first to find celebrity, second to make sure it does not know anyone

  • LC278 - First Bad Version - Get to middle and subdivide, while loop inclusive

  • LC297 - Serialize and Deserialize Binary Tree - In order traversal with X representing NULL

    • 要求序列化输出 list，那么就不能用字符形式表达空节点。确认了下树每个数值范围有限，面试官说INT_MAX可以用

  • LC301 Remove invalid parentheses DFS (res, s, index, stringbuilder, numl,numr,open )

  • LC304 Range Sum Query DP

  • LC311 Sparse Matrix Multiplication array[] or hashmap

  • LC314 Binary Tree Vertical Order traversal

  • LC348 Design Tic-tac-toe +1-1

  • LC350

  • Behavior Questions List
  • 标黑题目要会做
  • 回顾+写总结 ie Stack, Queue的methods

BQ：

  • Linkedin Internship:

    With Linkedin Marketing Solution, Ads API.

    Maintain Ads Database and support internal and external use of ads related data

    Team - > profit making

    My role was to implement a private logging system that can record personal identifiable info

    • Design phase: elasticsearch, couchbase, oracle database, security
      • Acquire large amount of info in a short period
    • Implemention phase: school projects tiny sizes VS the real big sizes
    • Distributed System/Hadoop

  • Richmond research:

    • Detect bird spiece based on image of it
    • SVM, CNN

  • Nacho Operating Ssytem

  • Why not linkedin? 1. Project harder than expected (security,mentor change) 2. Team not looking for new grad 3. I myself is not perfect

Where were you this summer?

  • Want to learn more so I was studyinging and traveling
  • Illness

Why Facebook?

  • Best place for engineering
  • Culture and feeling: young exciting challenging move fast

  • Instagram

  • What team? Ads, Payment, Distributed System
  • What question do you have for me?
    • Do you like working at fb and what part do you like the most?
  • use english version
  • ask, then write
  • Edge cases

culture; transparency, openness

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