I am trying to solve a leetcode type problem that is a practice problem that came with an upcoming code test I need to do for a job and I am having trouble with it. Can anyone help me understand whats going wrong?
I am essentially looking for the brute force option as I dont know algos/DS.
PROBLEM:
Write a function:
function solution(A);
that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A.
For example, given A = [1, 3, 6, 4, 1, 2], the function should return 5.
Given A = [1, 2, 3], the function should return 4.
Given A = [−1, −3], the function should return 1.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [1..100,000]; each element of array A is an integer within the range [−1,000,000..1,000,000].
HERE IS MY SOLUTION:
function solution(A) {
let newArray = A.sort(function(a, b){return a-b})
let lowestNumber = 1
for(i=0; i < newArray.length; i++) {
if(lowestNumber > newArray[0]) {
return lowestNumber
}
if(lowestNumber == newArray[i]) {
lowestNumber = lowestNumber + 1
}
if(i = newArray.length - 1) {
return lowestNumber
}
}
}
The below snippet isnt working like I expect it to. lowestNumber isnt being increased and also the loop is exiting here I believe.
if(lowestNumber == newArray[i]) {
lowestNumber = lowestNumber + 1
Thanks for your help!
I think your > should be <, and the = in if(i = newArray.length - 1) should be ===.
And lowestNumber > newArray[0] will always be true if the array contains a negative number, so 1 will be returned.
Your effort seems careless, so you are going to have to up your game for the interview.
const integers = [5, -345, 562456, 95345, 4, 232, 1, 2, 3, 7, -457];
function solution(A) {
let newArray = A.sort((a, b) => a - b);
let lowestNumber = 1;
for (let i = 0; i < newArray.length; i++) {
const n = newArray[i];
if (n > 0) {
if (lowestNumber < n) {
return lowestNumber;
} else {
lowestNumber = n + 1;
}
}
}
return lowestNumber;
}
console.log(solution(integers));You can do this in O(N) using a Map():
function solution(arr) {
const seen = new Map();
for (let i = 0; i < arr.length; i++) {
seen.set(arr[i]);
}
for (let i = 1; i <= arr.length + 1; i++) {
if (!seen.has(i)) return i;
}
return 1;
}
console.log(solution([1, 3, 6, 4, 1, 2])); //-> 5
console.log(solution([1, 2, 3])); //-> 4
console.log(solution([-1, -3])); //-> 1The fastest solution
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
if (!A) return 1;
A.sort();
if (A[A.length - 1] < 1) return 1;
const setA = new Set(A);
let length = setA.size;
for (let i = 1; i <= length; i++) {
if (!setA.has(i)) {
return i;
}
}
return length + 1;
}