c++面试题,数字范围包含关系判断。 - V2EX
PepperEgg
V2EX    C++

c++面试题,数字范围包含关系判断。

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  •   PepperEgg Nov 4, 2021 2237 views
    This topic created in 1654 days ago, the information mentioned may be changed or developed.
    C++
    给定一个 list<int> , 例如{1 ,21 ,55 ,99 ,111 ,10000 ,99999} 随机,依次递增。
    再给定一个 list<pair<int, int> > 数据为 {( 1 ,8 ),( 10 ,20 ),( 27 ,100 )} 随机,依次递增,每个 pair 不存在交集。中间可以有空缺。

    假定两列数据都大于 100w 条,如何快速列出第一个列表的数字存在于第二个列表中。
    比如 1 ,就属于(1,8),55 属于( 27 ,100 ),21 则不属于;
    有无最优解,求问大佬。
    8 replies    2021-11-05 08:44:54 +08:00
    iBugOne
        1
    iBugOne  
       Nov 4, 2021
    都排好序了还不直接扫描

    用归并排序中「归并一轮」这个操作的思路,你马上就知道第一个 list 里哪些数是夹在第二个 list 哪些数中间了
    zidian9
        2
    zidian9  
       Nov 4, 2021
    从前往后扫描,复杂度 O(m+n)
    JKeita
        3
    JKeita  
       Nov 4, 2021
    双指针遍历不就行了?
    JKeita
        4
    JKeita  
       Nov 4, 2021
    i:第一个列表指针
    j:第二个列表指针

    三种情况
    v < min(j): i++
    v >= min(j) && v <= max(j): i++
    v > max(j): j++
    NVDA
        5
    NVDA  
       Nov 4, 2021
    第二个列表如果排序了那就 binary search 找呗,最多是 mlogn
    Jooooooooo
        6
    Jooooooooo  
       Nov 4, 2021
    两个指针往前挪
    stcheng
        7
    stcheng  
       Nov 4, 2021
    1. 双指针 O(m+n)
    2. 二分搜索 O(m*log(N)) or O(n*log(m))
    根据 m 和 n 大小做选择
    byaiu
        8
    byaiu  
       Nov 5, 2021 via iPhone
    list 不能随机存取吧……
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