Maximum Deletions on a String — LeetCode 2430 Python Solution

The problem

You are given a string s consisting of only lowercase English letters. In one operation, you can: Delete the entire string s, or Delete the first i letters of s if the first i letters of s are equal to the following i letters in s, for any i in the range 1 <= i <= s.length / 2.

Example

Input

s = "abcabcdabc"

Output

2

Explanation

- Delete the first 3 letters ("abc") since the next 3 letters are equal. Now, s = "abcdabc".

Python solution

class Solution:
    def deleteString(self, s: str) -> int:
        @cache
        def dfs(i: int) -> int:
            if i == n:
                return 0
            ans = 1
            for j in range(1, (n - i) // 2 + 1):
                if s[i : i + j] == s[i + j : i + j + j]:
                    ans = max(ans, 1 + dfs(i + j))
            return ans

        n = len(s)
        return dfs(0)

Complexity

Pattern: Dynamic Programming

Define a state, write the transition, and stop recomputing the same subproblem. LeetCode 2430. Maximum Deletions on a String is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Dynamic Programming.

The dynamic programming guide has the Python template for the pattern and the 481 LeetCode problems that use it.

Related problems