PermMissingElem

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 A[1] = 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.

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https://codility.com/demo/results/trainingQPZDKX-KUK/

solution with sum aritmetic progresion

https://codility.com/demo/results/trainingGTC7SM-K39/

python 

https://codility.com/demo/results/trainingV84JT6-DZ2/

using System; // you can also use other imports, for example: // using System.Collections.Generic; // you can write to stdout for debugging purposes, e.g. // Console.WriteLine("this is a debug message"); class Solution { public int solution(int[] A) { uint N = (uint)A.Length + 1; // suma ciagu od 1 do N o n elementach UInt64 total = (UInt64) N * (N + 1) / 2; foreach (uint value in A) { total = total-value; } return (int)total; } }

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