```
def minimumDeleteSum(self, s1, s2):
"""
:type s1: str
:type s2: str
:rtype: int
"""
l1 = len(s1)
l2 = len(s2)
mtx = [ [0 for cols in range(l1+1)] for rows in range(l2+1) ]
for col in range(1,l1+1):
mtx[0][col] = mtx[0][col-1] + ord(s1[col-1])
for row in range(1,l2+1):
mtx[row][0] = mtx[row-1][0] + ord(s2[row-1])
for col in range(1,l1+1):
for row in range(1,l2+1):
if s1[col-1] == s2[row-1]:
mtx[row][col] = mtx[row-1][col-1]
else:
mtx[row][col] = min(mtx[row-1][col]+ord(s2[row-1]),mtx[row][col-1]+ord(s1[col-1]))
return mtx[-1][-1]
```

EDIT: not sure why but now it's accepting, it was throwing Time limit exceeded exception on the last test case, but now it accepted for the exact code,