Minimum ASCII Delete Sum for Two Strings

lcpy gen -n 712   # by problem number
lcpy gen -s minimum_ascii_delete_sum_for_two_strings   # by problem name

Input: s1 = "sea", s2 = "eat"
Output: 231
Explanation: Deleting "s" from "sea" adds the ASCII value of "s" (115) to the sum.
Deleting "t" from "eat" adds 116 to the sum.
At the end, both strings are equal, and 115 + 116 = 231 is the minimum sum possible to achieve this.

Input: s1 = "delete", s2 = "leet"
Output: 403
Explanation: Deleting "dee" from "delete" to turn the string into "let", adds 100[d] + 101[e] + 101[e] to the sum.
Deleting "e" from "leet" adds 101[e] to the sum.
At the end, both strings are equal to "let", and the answer is 100 + 101 + 101 + 101 = 403.

class Solution:
    # Time: O(m * n)
    # Space: O(min(m, n))
    def minimum_delete_sum(self, s1: str, s2: str) -> int:
        if len(s1) < len(s2):
            s1, s2 = s2, s1
        prev = [0] * (len(s2) + 1)
        for j in range(1, len(s2) + 1):
            prev[j] = prev[j - 1] + ord(s2[j - 1])
        for i in range(1, len(s1) + 1):
            curr = [prev[0] + ord(s1[i - 1])]
            for j in range(1, len(s2) + 1):
                if s1[i - 1] == s2[j - 1]:
                    curr.append(prev[j - 1])
                else:
                    curr.append(min(prev[j] + ord(s1[i - 1]), curr[j - 1] + ord(s2[j - 1])))
            prev = curr
        return prev[-1]