最長公共子序列 待研究

def lcs_len(a,b):
c = [[0 for j in b] for i in a]
for i in range(len(a)):
for j in range(len(b)):
if i==0 or j==0:
continue
if a[i]==b[j]:
c[i][j] = c[i-1][j-1]+1
else:
c[i][j] = max(c[i-1][j],c[i][j-1])
print(c)
return c[i][j]

print(lcs_len(‘dfdafasfadsfasdfsadf’,’dafasdfadsfkljfkldjasfkl’))

def lcs_string(a,b):
lena,lenb = len(a),len(b)

# length table
c = [[0 for i in b] for j in a]

# direction table
flag = [[0 for i in b] for j in a]

for i in range(lena):
    for j in range(lenb):
        if i==0 or j==0:           continue

        if a[i]==b[j]:
            c[i][j] = c[i-1][j-1]+1
            flag[i][j] = 3

        elif c[i-1][j]<c[i][j-1]:
            c[i][j] = c[i][j-1]
            flag[i][j] = 2
        else:
            c[i][j] = c[i-1][j]
            flag[i][j] = 1


(p1,p2) = (lena-1,lenb-1)
s = []
while 1:
    d = flag[p1][p2]
    if d == 3:
        s.append(a[p1])
        p1 -= 1
        p2 -= 1 
    elif d == 2:
        p2 -= 1
    elif d == 1:
        p1 -= 1
    if p1==0 or p2==0:
        # solve the first element without print problem
        if a[p1]==b[p2]:
            s.append(a[p1])
        break
s.reverse()
print(c)
return ''.join(s)

print(lcs_string(‘dfdafasfadsfasdfsadf’,’dafasdfadsfkljfkldjasfkl’))

問題：上面算的是12，下面是13，？？？？