Syntax error Program to check minimum number of characters needed to make string palindrome in Python

Program to check minimum number of characters needed to make string palindrome in Python

Suppose we have a string s, we have to find the minimum number of characters needed to be inserted so that the string becomes a palindrome.

So, if the input is like s = "mad", then the output will be 2, as we can insert "am" to get "madam".

To solve this, we will follow these steps −

  • Define a function dp(). This will take i, j

  • if i >= j, then

    • return 0

  • if s[i] is same as s[j], then

    • return dp(i + 1, j - 1)

  • otherwise,

    • return minimum of dp(i + 1, j) and dp(i, j - 1) + 1

  • From the main method, do the following

  • return dp(0, size of s - 1)

Let us see the following implementation to get better understanding −

Example

 Live Demo

class Solution:
   def solve(self, s):
      def dp(i, j):
         if i >= j:
            return 0
         if s[i] == s[j]:
            return dp(i + 1, j - 1)
         else:
            return min(dp(i + 1, j), dp(i, j - 1)) + 1
      return dp(0, len(s) - 1)
ob = Solution()
s = "mad"
print(ob.solve(s))

Input

s = "mad"

Output

2
Updated on: 2020-10-12T12:04:58+05:30

492 Views

Kickstart Your Career

Get certified by completing the course

Get Started
Advertisements