根據《算法導論》中提供的優化思想，在打印LCS時可以只用存儲結果的表格，所以就實現了下：
#coding=utf-8
''' Author:zhanglongqi
Date:2018-4-4
E-mail:[email protected]
Descrip:以求最長迴文序列爲背景，優化揹包思想中的打印結果序列
'''
def bag(nums):
mun=nums[::-1]
nums.insert(0,0)
mun.insert(0,0)
res=[[0 for i in range(len(nums)+1)] for j in range(len(mun)+1)]
for i in range(1,len(nums)):
for j in range(1,len(mun)):
if nums[i]==mun[j]:
res[i][j]=res[i-1][j-1]+1
elif res[i-1][j]>res[i][j-1]:
res[i][j]=res[i-1][j]
else:
res[i][j]=res[i][j-1]
return res
def prints(res,nums,i,j):
mun=nums[::-1]
nums.insert(0,0)
mun.insert(0,0)
if i>0 and j>0:
if res[i][j]==res[i-1][j-1]+1:
print(mun[i],end='')
prints(res,nums,i-1,j-1)
else:
if res[i-1][j]>res[i][j-1]:
prints(res,nums,i,j-1)
else:
prints(res,nums,i-1,j)
if __name__=='__main__':
s=['abcda','google']
for num in s:
print(num)
res=bag(list(num))
print(res[len(num)][len(num)])
prints(res,list(num),len(num),len(num))
print('\n')
Run-Demon:
