Program to find minimum required chances to form a string with K unique characters in Python

Suppose we have a string s of lowercase alphabet characters, and another number k, we have to find the minimum number of required changes in the string so that the resulting string has at most k distinct characters. In this case The change is actually changing a single character to any other character.

So, if the input is like s = "wxxyyzzxx", k = 3, then the output will be 1, as we can remove the letter "w" to get 3 distinct characters (x, y, and z).

To solve this, we will follow these steps −

  • count := a map of each character in s and their frequency

  • sv := sorted list of frequency values

  • ans := 0

  • for i in range 0 to (size of count) - k - 1, do

    • ans := ans + sv[i]

  • return ans

Let us see the following implementation to get better understanding −


 Live Demo

from collections import Counter
class Solution:
   def solve(self, s, k):
      count = Counter(s)
      sv = sorted(count.values())
      ans = 0
      for i in range(len(count) - k):
         ans += sv[i]
      return ans

ob = Solution()
s = "wxxyyzzxx"
k = 3
print(ob.solve(s, k))





Updated on: 09-Oct-2020


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