function printAllNumbersThenAllPairSums(numbers) { console.log("these are the numbers:"); numbers.forEach(function(number) { console.log(number); }); console.log("and these are their sums:"); numbers.forEach(function(firstNumber) { numbers.forEach(function(secondNumber) { console.log(firstNumber + secondNumber); }); }); } printAllNumbersThenAllPairSums([1, 2, 3, 4, 5]); // O(n^2)

//Give 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 arr1= ['a','b','c','x']; const arr2= ['z','y','x']; //should return True. //2 parameters - arrays- no size limit // return true or false //0(n^2) function containsCommonItem(arr1,arr2){ for (let i=0;i<arr1.lenght;i++){ for (let j=0; j<arr2.lenght;j++){ if(arr1[i]==arr2[j]){ return true; } } } return false }

// 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; } console.log(hasPairWithSum2([6,4,3,2,1,7], 9))