Minimum ASCII Delete Sum for Two Strings — LeetCode 712 Python Solution

The problem

Given two strings s1 and s2, return the lowest ASCII sum of deleted characters to make two strings equal.

Example

Input

s1 = "sea", s2 = "eat"

Output

231

Explanation

Deleting "s" from "sea" adds the ASCII value of "s" (115) to the sum.

Python solution

class Solution:
    def minimumDeleteSum(self, s1: str, s2: str) -> int:
        m, n = len(s1), len(s2)
        f = [[0] * (n + 1) for _ in range(m + 1)]
        for i in range(1, m + 1):
            f[i][0] = f[i - 1][0] + ord(s1[i - 1])
        for j in range(1, n + 1):
            f[0][j] = f[0][j - 1] + ord(s2[j - 1])
        for i in range(1, m + 1):
            for j in range(1, n + 1):
                if s1[i - 1] == s2[j - 1]:
                    f[i][j] = f[i - 1][j - 1]
                else:
                    f[i][j] = min(
                        f[i - 1][j] + ord(s1[i - 1]), f[i][j - 1] + ord(s2[j - 1])
                    )
        return f[m][n]

Complexity

Pattern: Dynamic Programming

Define a state, write the transition, and stop recomputing the same subproblem. LeetCode 712. Minimum ASCII Delete Sum for Two Strings 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.

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