Algorithm to find duplicate in an array

Question

I have an assignment to create an algorithm to find duplicates in an array which includes number values. but it has not said which kind of numbers, integers or floats. I have written the following pseudocode:

 FindingDuplicateAlgorithm(A) // A is the array
      mergeSort(A);
      for  int i <- 0 to i<A.length
           if A[i] == A[i+1]
                 i++
               return  A[i]
           else
                 i++

have I created an efficient algorithm? I think there is a problem in my algorithm, it returns duplicate numbers several time. for example if array include 2 in two for two indexes i will have ...2, 2,... in the output. how can i change it to return each duplicat only one time? I think it is a good algorithm for integers, but does it work good for float numbers too?

Answer 1

To handle duplicates, you can do the following:

if A[i] == A[i+1]:
    result.append(A[i]) # collect found duplicates in a list
    while A[i] == A[i+1]: # skip the entire range of duplicates 
        i++               # until a new value is found