Split String into K Distinct Partitions in Python

Suppose we have a string s and and a value k. The value of k is factor of the length of s, say the length is n. We can split s into n/k different substrings called t_i of size k. Then use these t_i to make u_i such that

• The characters present in u_i are subsequence of characters in t_i

• Any repeat characters will be removed from these string such that frequency of each character in u_i is 1

We have to find these u_i strings

So, if the input is like s = "MMPQMMMRM" k = 3, then the output will be ["MP", "QM", "MR"] because the size of s is 9, and k is 3, so 9/3 = 3. The strings are MMP, QMM and MRM, but as we do not support duplicate characters, then they will be MP, QM and MR.

To solve this, we will follow these steps −

• i := 0
• ret := a new list
• mp := a new map
• to_print := blank string
• while i < size of s, do
  • if i mod k is same as 0 and i is not 0, then
    • insert to_print at the end of ret
    • clear mp and clear to_print
  • if s[i] not present in mp, then
    • mp[s[i]] := 0
    • to_print := to_print + s[i]
  • i := i + 1
• insert to_print at the end of ret
• return ret

Example

Let us see the following implementation to get better understanding

def solve(s, k):
   i = 0
   ret = []
   mp, to_print = {}, ""
   while i < len(s):
      if i % k == 0 and i != 0:
         ret.append(to_print)
         mp, to_print = {}, ""
      if s[i] not in mp.keys():
         mp[s[i]] = 0
         to_print += s[i]
      i += 1
   ret.append(to_print)
   return ret

s = "MMPQMMMRM"
k = 3
print(solve(s, k))

Input

"MMPQMMMRM", 3

Output

['MP', 'QM', 'MR']