Question 401639 in Javascript Question posted in
A very good W3school tutorial can be found here.

What is the javascript alternative for 'unordered_set' / 'unordered_map' from c++, which give O(1) TC for 'search', 'insert' and 'delete'?

Is there any similar implementation of ‘unordered_set’ / ‘unordered_map’ from c++, in javascript?

C++ Implementation

void someFunction(vector<int> &arr, int k){
    unordered_set<int> s(arr.begin(), arr.end());
    
    auto it = s.find(k); // TC: O(1)
    if(it != s.end())
        s.erase(k); // TC: O(1)
    else
        s.insert(k); // TC: O(1)
}

JS alternative try…

function someFunction(arr, k){
    let s = new set(arr);
    
    if(s.has(k)) // TC = ?
        s.delete(k); // TC = ?
    else
        s.add(k); // TC = ?
}
Tags:

2

Answers


  1. 0

    You are close but you made it set where it should have been Set. See Set @ Mozilla.

    function someFunction(arr, k) {
  s = new Set(arr);

  if(s.has(k)) {
    console.log("deleting ", k);
    s.delete(k);
  } else {
    console.log("adding ", k);
    s.add(k);
  }
  
  return s;
}

var res = someFunction([1,2,3,4], 5);
console.log(Array.from(s)); // 1,2,3,4,5
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  2. 0

    TLDR: The javascript object type is effectively a map.

    let arr = [33,44,55,66];
let s = {}; // object declaration
let j = 33;
let k = 99;

// enumerate array and insert values
for (item of arr) {
    s[item] = true;
}

// search: s[item] will return undefined if item is not in object's map
// otherwise, if found, it will return the value at that key

console.log("j was " + (s[j] ? "found" : "not found"));
console.log("k was " + (s[k] ? "found" : "not found"));

// remove
delete s[j];

// insert
s[k] = true

console.log("-----");
console.log("j was " + (s[j] ? "found" : "not found"));
console.log("k was " + (s[k] ? "found" : "not found"));

    Also of note – Arrays are objects too in Javascript, So the array: [33,44,55,66] is mostly equivalent to:

    arr = {};
arr[0] = 33;
arr[1] = 44;
arr[2] = 55;
arr[3] = 66;
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