Program to find minimum swaps required to make given anagram in python

Suppose we have two strings S and T and they are anagrams of each other. We have to find the minimum number of swaps required in S to make it same as T.

So, if the input is like S = "kolkata" T = "katloka", then the output will be 3, as can swap in this sequence [katloka (given), kotlaka, koltaka, kolkata].

To solve this, we will follow these steps −

• Define a function util() . This will take S, T, i
• if i >= size of S , then
  • return 0
• if S[i] is same as T[i], then
  • return util(S, T, i + 1)
• x := T[i]
• ret := 99999
• for j in range i + 1 to size of T, do
  • if x is same as S[j], then
    • swap S[i] and S[j]
    • ret := minimum of ret and (1 + util(S, T, i + 1))
    • swap S[i] and S[j]
• return ret
• From the main method do the following:
• return util(S, T, 0)

Let us see the following implementation to get better understanding −

Example 

Live Demo

class Solution:
   def util(self, S, T, i) :
      S = list(S)
      T = list(T)
      if i >= len(S):
         return 0
      if S[i] == T[i]:
         return self.util(S, T, i + 1)
      x = T[i]
      ret = 99999;
      for j in range(i + 1, len(T)):
         if x == S[j]:
            S[i], S[j] = S[j], S[i]
            ret = min(ret, 1 + self.util(S, T, i + 1))
            S[i], S[j] = S[j], S[i]
      return ret
     
   def solve(self, S, T):
      return self.util(S, T, 0)

ob = Solution()
S = "kolkata"
T = "katloka"
print(ob.solve(S, T))

Input

"kolkata", "katloka"

Output

3