在保持顺序的同时用“精简”列表替换列表

小编典典

在保持顺序的同时用“精简”列表替换列表

algorithm

我有一个清单清单，如我所附的代码所示。如果有任何公共值，我想链接每个子列表。然后，我想用压缩的列表列表替换列表列表。 示例：
如果我有一个列表，[[1,2,3],[3,4]]我想要[1,2,3,4]。如果我有[[4,3],[1,2,3]]我想要的[4,3,1,2]。如果我有[[1,2,3],[a,b],[3,4],[b,c]]我想要的，[[1,2,3,4],[a,b,c]]或者[[a,b,c],[1,2,3,4]]我不在乎哪一个。

我快到了…

我的问题是，当我有一个[[1,2,3],[10,5],[3,8,5]]想要的案例，[1,2,3,10,5,8]但使用当前代码时，[1,2,3,8,10,5]

这是我的代码：

import itertools

a = [1,2,3]
b = [3,4]
i = [21,22]
c = [88,7,8]
e = [5,4]
d = [3, 50]
f = [8,9]
g=  [9,10]
h = [20,21]

lst = [a,b,c,i,e,d,f,g,h,a,c,i]*1000  
#I have a lot of list but not very many different lists

def any_overlap(a, b):
  sb = set(b)
  return any(itertools.imap(sb.__contains__, a))

def find_uniq(lst):
    ''' return the uniq parts of lst'''
    seen = set()
    seen_add = seen.add
    return [ x for x in lst if x not in seen and not seen_add(x)]

def overlap_inlist(o_lst, lstoflst):
    '''
    Search for overlap, using "any_overlap", of a list( o_lst) in a list of lists (lstoflst).
    If there is overlap add the uniq part of the found list to the search list, and keep 
    track of where that list was found 
    '''
    used_lst =[ ]
    n_lst =[ ]
    for lst_num, each_lst in enumerate(lstoflst):
        if any_overlap(o_lst,each_lst):
            n_lst.extend(each_lst)
            used_lst.append(lst_num)
    n_lst= find_uniq(n_lst)
    return  n_lst, used_lst

def comb_list(lst):
    '''
    For each list in a list of list find all the overlaps using 'ovelap_inlist'.
    Update the list each time to delete the found lists. Return the final combined list. 
    '''
    for updated_lst in lst:
        n_lst, used_lst = overlap_inlist(updated_lst,lst)
        lst[:] = [x for i,x in enumerate(lst) if i not in used_lst]
        lst.insert(0,n_lst)
    return lst
comb_lst = comb_list(lst)
print comb_lst

该脚本的输出是：

[[88, 7, 8, 9, 10], [1, 2, 3, 4, 50, 5], [21, 22, 20]]

我想要它，所以密钥按原始顺序排列：

[[88, 7, 8, 9, 10], [1, 2, 3, 4, 5, 50,], [21, 22, 20]]

在 5和50切换 在新LST [2]

我对python有点陌生。对于该问题的任何解决方案或对当前代码的评论，我将不胜感激。我不是计算机科学家，我想可能会有某种算法能够快速地做到这一点（也许是从集合论出发？）。如果有这样的算法，请指出正确的方向。

我可能会让这种方式变得更复杂，然后呢……谢谢！！

阅读 223

2020-07-28

共1个答案

小编典典

这是一种蛮力方法（可能更容易理解）：

from itertools import chain

def condense(*lists):
    # remember original positions
    positions = {}
    for pos, item in enumerate(chain(*lists)):
        if item not in positions:
            positions[item] = pos

    # condense disregarding order
    sets = condense_sets(map(set, lists))

    # restore order
    result = [sorted(s, key=positions.get) for s in sets]
    return result if len(result) != 1 else result[0]

def condense_sets(sets):
    result = []
    for candidate in sets:
        for current in result:
            if candidate & current:   # found overlap
                current |= candidate  # combine (merge sets)

                # new items from candidate may create an overlap
                # between current set and the remaining result sets
                result = condense_sets(result) # merge such sets
                break
        else:  # no common elements found (or result is empty)
            result.append(candidate)
    return result

例

>>> condense([1,2,3], [10,5], [3,8,5])
[1, 2, 3, 10, 5, 8]
>>> a = [1,2,3]
>>> b = [3,4]
>>> i = [21,22]
>>> c = [88,7,8]
>>> e = [5,4]
>>> d = [3, 50]
>>> f = [8,9]
>>> g=  [9,10]
>>> h = [20,21]
>>> condense(*[a,b,c,i,e,d,f,g,h,a,c,i]*1000)
[[1, 2, 3, 4, 5, 50], [88, 7, 8, 9, 10], [21, 22, 20]]
>>> condense([1], [2, 3, 2])
[[1], [2, 3]]

性能比较

condense_*()函数来自于该问题的答案。lst_OP来自问题的输入列表（不同大小），lst_BK-来自@Blckknght答案的测试列表（不同大小）。请参阅源代码。

测量表明，基于“不相交集”和“无向图的连接组件”概念的解决方案在两种输入类型上的执行效果均相似。

name                       time ratio comment
condense_hynekcer     5.79 msec  1.00 lst_OP
condense_hynekcer2     7.4 msec  1.28 lst_OP
condense_pillmuncher2 11.5 msec  1.99 lst_OP
condense_blckknght    16.8 msec  2.91 lst_OP
condense_jfs            26 msec  4.49 lst_OP
condense_BK           30.5 msec  5.28 lst_OP
condense_blckknght2   30.9 msec  5.34 lst_OP
condense_blckknght3   32.5 msec  5.62 lst_OP


name                       time  ratio comment
condense_blckknght     964 usec   1.00 lst_BK
condense_blckknght2   1.41 msec   1.47 lst_BK
condense_blckknght3   1.46 msec   1.51 lst_BK
condense_hynekcer2    1.95 msec   2.03 lst_BK
condense_pillmuncher2  2.1 msec   2.18 lst_BK
condense_hynekcer     2.12 msec   2.20 lst_BK
condense_BK           3.39 msec   3.52 lst_BK
condense_jfs           544 msec 563.66 lst_BK


name                       time ratio comment
condense_hynekcer     6.86 msec  1.00 lst_rnd
condense_jfs          16.8 msec  2.44 lst_rnd
condense_blckknght    28.6 msec  4.16 lst_rnd
condense_blckknght2   56.1 msec  8.18 lst_rnd
condense_blckknght3   56.3 msec  8.21 lst_rnd
condense_BK           70.2 msec 10.23 lst_rnd
condense_pillmuncher2  324 msec 47.22 lst_rnd
condense_hynekcer2     334 msec 48.61 lst_rnd

要重现结果，请克隆要点并运行measure- performance-condense- lists.py

2020-07-28