python 最长公共子序列

网上有很多，但有bug，特别是这个：http://www.oschina.net/code/snippet_16840_2015　好大的坑...

get length

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])
return c[i][j]

get string

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()
return ''.join(s)

use into app

def lcs_from_list(input,jobnames):
if input in jobnames:
return input
res = [(lcs_len(input,jobname),jobname) for jobname in jobnames]
res.sort()
return res[-1][1]