Unique Number of Occurrences in Python

Suppose we have an array. We have to check whether each element has unique number of occurrences. If no such element is present then return false, otherwise true. So if the array is like [1, 1, 2, 2, 2, 3, 4, 4, 4, 4], then it will return true as the element 1 is present two times, 2 is present three times, 3 is present once and 4 is present four times.

To solve this, we will follow these steps −

  • We will find the frequency of elements of the array
  • for each key-value pair in the frequency map
    • if value is present in another map mp, then return false
    • put mp[value] := 1
  • return true


Let us see the following implementation to get better understanding −

 Live Demo

class Solution(object):
   def uniqueOccurrences(self, arr):
      d = {}
      for i in arr:
         if i not in d:
            d[i] =1
      l = {}
      for x, y in d.items():
         if y in l:
            return False
         l[y] = 1
      return True
ob1 = Solution()