Minimum Operations to Make One String Substring of Another in Python

Suppose we have two strings s and t, we have to find the minimum amount of operations required for s to make t a substring of s. Now, in each operation, we can choose any position in s and change the character at that position to any other character.

So, if the input is like s = "abbpqr", t = "bbxy", then the output will be 2, as we can take the substring "bbpq" and change 'p' to 'x' and 'q' to 'y'.

To solve this, we will follow these steps −

• k := size of t, n := size of s
• ans := 10^10
• for i in range 0 to n - k, do
  • ss := substring of s[from index i to i+k-1]
  • ans := minimum of ans and number of unmatched character of s and t
• return ans

Let us see the following implementation to get better understanding −

Example

 Live Demo

class Solution:
   def solve(self, s, t):
      k, n = len(t), len(s)
      ans = 10**10
      for i in range(n - k + 1):
         ss = s[i:i+k]
         ans = min(ans, sum(ss[j]!=t[j] for j in range(k)))
      return ans
ob = Solution()
print(ob.solve("abbpqr", "bbxy"))

Input

"abbpqr", "bbxy"

Output

2