common child hackerrank solution
def commonChild(s1, s2):
m = [[0]*(len(s2)+1) for _ in range(len(s1)+1)]
for i,c in enumerate(s1,1):
for j,d in enumerate(s2,1):
if c == d:
m[i][j] = m[i-1][j-1]+1
else:
m[i][j] = max(m[i][j-1],m[i-1][j])
return m[-1][-1]
print(commonChild(input(), input()))