Interview question - Big O

// Given 2 arrays, create a function that let's a user know (true/false) whether these two arrays contain any common items

//For Example:

//const array1 = ['a', 'b', 'c', 'x'];//const array2 = ['z', 'y', 'i'];

//should return false.

//-----------

// const array1 = ['a', 'b', 'c', 'x'];

// const array2 = ['z', 'y', 'x'];

//should return true.

// 2 parameters - arrays - no size limit

// return true or false

function containsCommonItem(arr1, arr2) {

for (let i=0; i < arr1.length; i++) {

for ( let j=0; j < arr2.length; j++) {

if(arr1[i] === arr2[j]) {

return true;

}

}

}

return false

}

//O(a*b)

//O(1) - Space Complexity

const array1 = ['a', 'b', 'c', 'x'];

const array2 = ['z', 'y', 'a'];

function containsCommonItem2(arr1, arr2) {

// loop through first array and create object where properties === items in the array

// can we assume always 2 params?

let map = {};

for (let i=0; i < arr1.length; i++) {

if(!map[arr1[i]]) {

const item = arr1[i];

map[item] = true;

}

}

// loop through second array and check if item in second array exists on created object.

for (let j=0; j < arr2.length; j++) {

if (map[arr2[j]]) {

return true;

}

}

return false

}

//O(a + b) Time Complexity

//O(a) Space Complexity

// containsCommonItem2(array1, array2)

function containsCommonItem3(arr1, arr2) {

return arr1.some(item => arr2.includes(item))

}

containsCommonItem(array1, array2)

containsCommonItem2(array1, array2)

containsCommonItem3(array1, array2)