Javascript algorithms and data structures

Question 1

Explain the frequency counter pattern

Answer 1

Useful for avoiding O(N^2) with arrays and strings.

Counts frequency of specific item and add it to an object.

Good example is to check if 2 strings are anagrams of each other.

const same = function(string1, string2){
const counter1={};
const counter2={};

string1.split(‘’).forEach(letter=>{
if(counter1[letter]) counter1[letter]++;
counter1[letter]=1;
})

string2.split(‘’).forEach(letter=>{
if(counter2[letter]) counter2[letter]++;
counter2[letter]=1;
})

// then check if counter1 and counter 2 are the same

}

Question 2

What is recursion?

Answer 2

It is when a function calls itself until a certain base case is met. The base case ensures that it doesn’t continue infinitely.

Question 3

Multiple pointer pattern

Answer 3

Have two pointers, each referencing a given index in an array to start with. Move these pointers in a way to solve a problem.

Use a while loop