Python 怎么实现归并集合功能? - V2EX
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zealinux

Python 怎么实现归并集合功能?

  •  
  •   zealinux Mar 13, 2019 306 views
    This topic created in 2641 days ago, the information mentioned may be changed or developed.

    比如

    输入:[(A, B), (B, C), (X,Y)] 输出:[(A, B, C), (X, Y)] 

    即归并有相同元素的集合。

    有没有现成的库?

    或者自己实现的化思路是什么样的?

    Supplement 1    Mar 13, 2019
    为求表示简单,省略 set(),
    A,A 指代同一字符串,比如” UUID_A"
    13 replies    2019-03-13 20:38:59 +08:00
    niknik
        1
    niknik  
       Mar 13, 2019
    楼下帮我回一下,我上个厕所
    shyrock
        2
    shyrock  
       Mar 13, 2019
    这不是元组列表吗。。。哪里有集合。。。
    bumz
        3
    bumz  
       Mar 13, 2019
    并查集?
    bumz
        4
    bumz  
       Mar 13, 2019
    @shyrock #2 逻辑上的集合
    ybbswc
        5
    ybbswc  
       Mar 13, 2019 via Android
    首先判断是否有相同元素,有的话就作并集。楼下来吧。(;)
    bumz
        6
    bumz  
       Mar 13, 2019
    亲测并查集可行,复杂度 O(n),n 为输入中唯一元素的个数 * 每种元素平均出现次数

    https://gist.github.com/bumfo/26fc4865e27b48385ed650cd08fe6004
    bumz
        7
    bumz  
       Mar 13, 2019
    @bumz #6 想要 set 的话把 tuple 改成 set 一样
    bumz
        8
    bumz  
       Mar 13, 2019
    @bumz #6 复杂度 O(n log m),m 是不同元素的个数,n 是 m * 每个元素的平均出现次数
    bumz
        9
    bumz  
       Mar 13, 2019
    @ybbswc #5 这种做法复杂度 O(ab), a 是集合的个数,b 是每个集合中元素的个数的平均值
    freemoon
        10
    freemoon  
       Mar 13, 2019
    ```
    a = [(1,2), (2,3)]
    b = [(1,2)]

    print(set(a) | set(b))
    ```
    strict
        11
    strict  
       Mar 13, 2019
    复杂度目前想到的全是 m*n
    xor
        12
    xor  
       Mar 13, 2019 via iPhone
    @strict 并查集可以 n log m
    xor
        13
    xor  
       Mar 13, 2019 via iPhone
    @xor 并查集可以做到在现实中 O(m)
    严格来讲 O(m α(n)) 但是现实中 α(n) <= 4
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