Codility -

 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:

class Solution { public int solution(int[] 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)].

 using System;

using System.Linq;

using System.Collections.Generic;

// 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) {

        // write your code in C# 6.0 with .NET 4.5 (Mono)

        //Array.Sort(A);

        List<int> list = A.ToList();

        int min = list.Min();

        int max = list.Max();

        int result = min;

        while(result < max){

            if(!list.Contains(result)) return result;

            result = result + 1;

        }

        return result;

    }

}