Syntax error Program to count number of operations needed to make string as concatenation of same string twice in Python

Program to count number of operations needed to make string as concatenation of same string twice in Python

Suppose we have a lowercase string s. Now consider an operation, where we can delete, insert or update any character in s. We have to count minimum number of operations required to make s = (t concatenate t) for any string t.

So, if the input is like s = "pqrxqsr", then the output will be 2, because, we can update the "x" with "p" and delete "s", then s is "pqrpqr", this is s = t concatenate t, for t = "pqr".

To solve this, we will follow these steps −

  • Define a function edit_distance(). This will take s1, s2
  • m := size of s1
  • n := size of s2
  • cur := a new list from range 0 to n
  • for i in range 0 to m - 1, do
    • prev := cur
    • cur := a list with (i + 1) and then n number of 0s
    • for j in range 0 to n - 1, do
      • cur[j + 1] := prev[j] if s1[i] and s2[j] are same otherwise (minimum of cur[j], prev[j], prev[j + 1]) + 1
  • return cur[n]
  • From the main method, do the following −
  • res := size of s
  • for i in range 0 to size of s - 1, do
    • res := minimum of edit_distance(substring of s from index 0 to i - 1, substring of s from index i to end) and res
  • return res

Example

Let us see the following implementation to get better understanding −

def solve(s):
   def edit_distance(s1, s2):
      m, n = len(s1), len(s2)
      cur = list(range(n + 1))
      for i in range(m):
         prev, cur = cur, [i + 1] + [0] * n
         for j in range(n):
            cur[j + 1] = (prev[j]
            if s1[i] == s2[j] else min(cur[j], prev[j], prev[j + 1]) + 1)
         return cur[n]

   res = len(s)
   for i in range(len(s)):
      res = min(edit_distance(s[:i], s[i:]), res)
   return res

s = "pqrxqsr"
print(solve(s))

Input

"pqrxqsr"

Output

None
Updated on: 2021-10-18T12:27:50+05:30

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