#!usr/bin/env python 
#encoding:utf-8 
 
''''' 
__Author__:沂水寒城 
功能：寻找最长回文子序列 
''' 
 
def slice_window(one_str,w=1): 
  ''''' 
  滑窗函数 
  ''' 
  res_list=[] 
  for i in range(0,len(one_str)-w+1): 
    res_list.append(one_str[i:i+w]) 
  return res_list 
 
 
def is_huiwen(one_str_list):  
  ''''' 
  输入一个字符串列表，判断是否为回文序列 
  '''  
  if len(one_str_list)==1:  
    return True   
  else:  
    half=len(one_str_list)/2  
    if len(one_str_list)%2==0:  
      first_list=one_str_list[:half]  
      second_list=one_str_list[half:]  
    else:  
      first_list=one_str_list[:half]  
      second_list=one_str_list[half+1:]  
    if first_list==second_list[::-1]:  
      return True   
    else:  
      return False  
 
 
def find_longest_sub_palindrome_str(one_str): 
  ''''' 
  主函数,寻找最长回文子序列 
  ''' 
  all_sub=[] 
  for i in range(1,len(one_str)): 
    all_sub+=slice_window(one_str,i) 
  all_sub.append(one_str) 
  new_list=[] 
  for one in all_sub: 
    if is_huiwen(list(one)): 
      new_list.append(one) 
  new_list.sort(lambda x,y:cmp(len(x),len(y)),reverse=True) 
  print new_list[0] 
 
 
if __name__ == '__main__': 
  one_str_list=['uabcdcbaop','abcba','dmfdkgbbfdlg','mnfkabcbadk'] 
  for one_str in one_str_list: 
    find_longest_sub_palindrome_str(one_str)