new_contents: class Solution(object):
      def minimumDeleteSum(self, s1, s2):
          """
          :type s1: str
          :type s2: str
          :rtype: int
          """
          prev = [0]
          for c in s2:
              prev.append(prev[-1] + ord(c))
          for i1, c1 in enumerate(s1, 1):
              nxtRow = [0] * (len(s2) + 1)
              o1 = ord(c1)
              nxtRow[0] = o1 + prev[0]
              for i2, c2 in enumerate(s2, 1):
                  if c1 == c2:
                      nxtRow[i2] = prev[i2 - 1]
                  else:
                      o2 = ord(c2)
                      nxtRow[i2] = min(prev[i2] + o1, nxtRow[i2 - 1] + o2)
              prev = nxtRow
          return nxtRow[len(s2)]
  
subject: Add py solution for 712. Minimum ASCII Delete Sum for Two Strings