// 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)
// Naive
function hasPairWithSum(arr, sum){
var len = arr.length;
for(var i =0; i<len-1; i++){
for(var j = i+1;j<len; j++){
if (arr[i] + arr[j] === sum)
return true;
}
}
return false;
}
// Better
function hasPairWithSum2(arr, sum){
const mySet = new Set();
const len = arr.length;
for (let i = 0; i < len; i++){
if (mySet.has(arr[i])) {
return true;
}
mySet.add(sum - arr[i]);
}
return false;
}
hasPairWithSum2([6,4,3,2,1,7], 9)
