Program to check whether palindrome can be formed after deleting at most k characters or not in python

Suppose we have a string s, we have to check whether we can make this string a palindrome after deleting at most k characters or not.

So, if the input is like s = "lieuvrel", k = 4, then the output will be True, we can delete three characters to get palindrome "level".

To solve this, we will follow these steps −

• Define a function lcs() . This will take a, b
• m := size of a, n := size of b
• table := matrix of size (m + 1) x (n + 1) and fill with 0
• for i in range 1 to m, do
  • for j in range 1 to n, do
    • if a[i - 1] is same as b[j - 1], then
      • table[i, j] := 1 + table[i - 1, j - 1]
    • otherwise,
      • table[i, j] := maximum of table[i, j - 1] and table[i - 1, j]
• return table[m, n]
• From the main method do the following:
• return true when (size of s - lcs(s, reverse of s) <= k) otherwise false

Let us see the following implementation to get better understanding −

Example 

Live Demo

class Solution:
   def solve(self, s, k):
      def lcs(a, b):
         m, n = len(a), len(b)
         table = [[0] * (n + 1) for _ in range(m + 1)]
         for i in range(1, m + 1):
            for j in range(1, n + 1):
               if a[i - 1] == b[j - 1]:
                  table[i][j] = 1 + table[i - 1][j - 1]
               else:
                  table[i][j] = max(table[i][j - 1], table[i - 1][j])
         return table[m][n]

      return len(s) - lcs(s, s[::-1]) <= k
     
ob = Solution()
s = "lieuvrel"
k = 4
print(ob.solve(s, k))

Input

"lieuvrel", 4

Output

True

Arnab Chakraborty

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Updated on: 03-Dec-2020

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