This is my solution to the PermMissingElem problem, I wonder what can be improved? Expected worst case time complexity is O(N), but the performance test shows that it's O(N) or O(N * log(N)), which I suppose there's some solution out there that can truly achieve pure O(N)?
function solution(A) {
const size = A.length;
let sum = 0;
for (i=0;i<size;i++){
sum += A[i];
}
return (((size+ 1)*(size + 2))/2) - sum
}
The original problem is quoted as follows:
A zero-indexed array A consisting of N different integers is given. The array contains integers in the range [1..(N + 1)], which means that exactly one element is missing.
Your goal is to find that missing element.
Write a function:
int solution(int A[], int N); that, given a zero-indexed array A, returns the value of the missing element.
For example, given array A such that:
A[0] = 2 A1 = 3 A[2] = 1 A[3] = 5 the function should return 4, as it is the missing element.
Assume that:
N is an integer within the range [0..100,000]; the elements of A are all distinct; each element of array A is an integer within the range [1..(N + 1)].
Complexity:
expected worst-case time complexity is O(N); expected worst-case space complexity is O(1), beyond input storage (not counting the storage required for input arguments). Elements of input arrays can be modified.