Program to count number of sublists with exactly k unique elements in Python

Suppose we have a list of numbers called nums and another value k, we have to find the number of sublists required that there are exactly k unique numbers in the sublist.

So, if the input is like nums = [2, 2, 3, 4] k = 2, then the output will be 3, as we have the sublists like: [2, 2, 3], [2, 3], [3, 4].

To solve this, we will follow these steps −

• Define a function count() . This will take K
• slot := an empty map, by default all values are 0
• i := res := 0
• for each index j, and value x nums, do
  • slot[x] := slot[x] + 1
  • while size of slot > K, do
    • slot[nums[i]] := slot[nums[i]] - 1
    • if slot[nums[i]] is same as 0, then
      • remove slot[nums[i]]
    • i := i + 1
  • res := res + j - i + 1
• return res
• From the main method do the following −
• return count(k) - count(k - 1)

Example (Python)

Let us see the following implementation to get better understanding −

from collections import Counter class Solution:    def solve(self, nums, k):       def count(K):          slot = Counter()          i = res = 0          for j, x in enumerate(nums):             slot[x] += 1             while len(slot) > K:                slot[nums[i]] -= 1                if slot[nums[i]] == 0:                   del slot[nums[i]]                i += 1             res += j - i + 1          return res       return count(k) - count(k - 1) ob = Solution() nums = [2, 2, 3, 4] k = 2 print(ob.solve(nums, k))

Input

[2, 2, 3, 4], 2

Output

3