Problem: PermMissingElem

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:

int solution(int A[], int N);

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)].
int solution(int A[], int N)  
{     
   int fV = 0,cV=0;      
   for(int i=1;i<=N+1;i++)         
      fV+=i;      
   for(int i=0;i<N;i++)         
      cV +=A[i];      
   return fV-cV; 
}

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