PermMissingElem

PermMissingElem

Find the missing element in a given permutation.

An 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:

function solution(A);

that, given an array A, returns the value of the missing element.

For example, given array A such that:

A[0] = 2
A[1] = 3
A[2] = 1
A[3] = 5
the function should return 4, as it is the missing element.

Write an efficient algorithm for the following assumptions:

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)].
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• 문제는 여기에

나의 풀이

function solution(A) {
    const expectedSum = (A.length + 1) * (A.length + 2) / 2;
    const realSum = A.reduce((a, b) => a + b, 0);
    return expectedSum - realSum;
}