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LeetCode Note
  • Introduction
  • Tools
    • Clean Code
    • 英文小辭典
    • JS Reference
    • 常見 Edge Case
    • Array Method
    • Object Method
    • Function
    • Hashing
    • Prototype
    • 處理 Array 小撇步
    • String Method
    • Math / Date
    • loop
    • JSON.xx / localStorage
    • Date
    • Regex
    • Memorization
    • reduce condition
    • 命名
  • 筆記 Note
    • Promise
    • Walking the DOM
    • Element size and scrolling
    • CSS
  • Leetcode todo
    • ToDo
  • Array
    • # Select random poker without duplicates
    • # 最少替換達成不連續字串
    • # 724 Find Pivot Index
    • # 747. Largest Number At Least Twice of Others
    • # 01 getMaxProfit
    • # maxOfBiggestVal
    • # findSecondLargest
    • # 41 First Missing Positive
    • # 134 Gas Station (有圖)
    • # 202 Happy Number
    • # 344 Reverse String
    • # 412 Fizz Buzz
    • # 561 Array Partition I
    • # 804 Unique Morse Code Words
    • # 905 Sort Array By Parity
    • # 121. Best Time to Buy and Sell Stock.js
    • # 122 Best Time to Buy and Sell Stock II
    • # 189 Rotate Array
    • # 229 Majority Element II
    • # 268 Missing Number.
    • # 299 Bulls and Cows (有圖)
    • # 896 Monotonic Array
    • # 1002 Find Common Characters
    • # 1051 Height Checker
    • # 1185 Day of the Week
    • # 169 Majority Element
    • # 605. Can Place Flowers
    • # 350 Intersection of Two Arrays II (有圖)
    • # 482. License Key Formatting
  • Set / Map
    • # GetLengthOfLongestSubstring
    • #1 Two Sum
    • # 217 Contains Duplicate
    • # 1122 Relative Sort Array
    • # 1160 Find Words That Can Be Formed by Characters
    • #811 Subdomain Visit Count
    • # 349 Intersection of Two Arrays
    • # 819 Most Common Word
  • Two Pointer
    • #704. Binary Search
    • #26 Remove Duplicates from Sorted Array (有圖)
    • #27 Remove Element
    • # 66 Plus One
    • # 80 Remove Duplicates from Sorted Array II (有圖)
    • # 88 Merge Sorted Array (有圖)
    • # 125 Valid Palindrome
    • #167 Two Sum II - Input array is sorted (有圖)
    • # 283 Move Zeroes (有圖)
    • # 38 Count and Say
    • # 557. Reverse Words in a String III
    • #977 Squares of a Sorted Array
    • #209 Minimum Size Subarray Sum
  • String
    • # 13 Roman to Integer (有圖)
    • # 771 Jewels and Stones
    • # 937 Reorder Data in Log Files
    • # 929 Unique Email Addresses
    • # 1108 Defanging an IP Address
    • #14 Longest Common Prefix
    • # 387 First Unique Character in a String (有圖)
    • #193 Valid Phone Numbers
    • # 28 Implement strStr()
    • #383 Ransom Note
  • Stack
    • # 20 Valid Parentheses (有圖)
    • # 155 Min Stack
    • BF 165. remove characters
    • #1047 Remove All Adjacent Duplicates In String
  • Binary Search
    • # 1064 Fixed Point (有圖)
    • # 852 Peak Index in a Mountain Array
  • Recursion 遞迴
    • #2625. Flatten Deeply Nested Array
  • Math
    • # 7 Reverse Integer
    • # 9 Palindrome Number (有圖)
    • #53 Maximum Subarray (有圖)
    • # 1085 Sum of Digits in the Minimum Number.
    • # 136 Single Number
    • # 204 Count Primes (有圖)
    • #243 Shortest Word Distance
  • Dynamic Programing
    • # 322 Coin Change
    • # 509 Fibonacci Number (有圖)
    • # 70 Climbing Stairs
    • # 198 House Robber
    • # 168. Excel Sheet Column Title
  • Others
    • # 205. Isomorphic Strings
    • Implement js Array method
    • Flatten Array/Object
  • Matrix
    • 867. Transpose Matrix
  • Queue
    • DOM tree with queue
  • 排序
    • Different Sort
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  • Set
  • Map
  • 其他

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  1. Tools

Hashing

Set/Map

Method
Set
Map
Big O

Init

new Set(['1','2']);

new Map([ [0,1],[0,2] ]);

增加

mySet.add('1')

myMap.set(0, 1)

O(1)

刪除

mySet.delete('1')

myMap.delete(0)

O(1)

清掉

mySet.clear()

myMap.clear()

取值

-

mySet.get(0) // 1

O(1)

是否存在

mySet.has('1')

myMap.has(0)

O(1)

長度

mySet.size

myMap.size

轉陣列

[...mySet]

[...myMap.values()]

Set

// ES6 Set
let instruments = new Set();
// or 一開始就把值存進去
let instruments = new Set(['1','2']);


instruments.add('piano');
instruments.has('guitar'); // false
instruments.delete('guitar'); // 裡面根本沒有 guitar 所以回傳 false
instruments.size; // 1
[...instruments] //['piano']

// or use Array.from, 
Array.from(instruments); 

Map

let myMap= new Map();

// or 一開始就存值,記得是 [[]] double array
let myMap = new Map([[keyString ,'value']]);

var keyString = 'I am string',
    keyObj = {},
    keyFunc = function() {},
    keyNumber = 1

// 增加
myMap.set(keyString , 'string value');
myMap.set(keyObj, {obj: 1});
myMap.set(keyFunc , function(){console.log('I am function')});
myMap.set(keyNumber , 100);

// 有幾個
myMap.size; // 4

// 取值
myMap.get(keyObj); // {obj: 1}

// 看是否存在
myMap.has(keyString ); //  true

// 刪掉
myMap.delete(keyNumber); 
myMap.size; // 3

// 轉陣列
[...myMap.values()] // ["string value", {obj: 1}, ƒ]

其他

if( lookup.has(str) ){
    lookup.set(str, lookup.get(str) + 1 )
} else {
    lookup.set(str, 1 )
}

可以改寫更簡短

lookup.set(str, (lookup.get(str) ?? 0) + 1 )

以下同理

if( !lookup.has(sortStr) ){
    lookup.set(sortStr, [str] )
} else {
     lookup.set(sortStr, [...lookup.get(sortStr), str] )
}

// 可以變以下
lookup.set(sortStr, [...(lookup.get(sortStr) ?? []), str] )
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Last updated 10 months ago

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