千万条记录的数组找 Top100,什么算法时间复杂度较低 - V2EX
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wangfyyy

千万条记录的数组找 Top100,什么算法时间复杂度较低

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  •   wangfyyy Jun 15, 2020 2791 views
    This topic created in 2145 days ago, the information mentioned may be changed or developed.

    时间复杂度最好小于 O(nlogn)

    8 replies    2020-07-04 06:10:34 +08:00
    Kilerd
        1
    Kilerd  
       Jun 15, 2020
    限制 nLogN 那就快排一下,取前 100 (反正你也没要求空间复杂度
    xupefei
        2
    xupefei  
       Jun 15, 2020 via iPhone
    heap sort,复杂度 n log100
    Perry
        3
    Perry  
       Jun 15, 2020 via iPhone
    先找到没有排好的 top 100
    B1ankCat
        4
    B1ankCat  
       Jun 15, 2020
    按理论来说最小堆就行
    takemeaway
        5
    takemeaway  
       Jun 15, 2020
    O(1)即可
    unixeno
        6
    unixeno  
       Jun 15, 2020 via Android
    构建一个 100 元素的小顶堆
    然后遍历数组,大于堆顶元素的时候就交换,然后调整堆
    wangfyyy
        7
    wangfyyy  
    OP
       Jun 15, 2020
    看来这不是一道经典的面试题
    yishanhe
        8
    yishanhe  
       Jul 4, 2020
    其实用堆的话 ,空间复杂度 是 O(k) 时间复杂度是 O(nlogk)
    这里的 k 就是 100
    已经比 O(nlogn) 小了

    如果要找比 O(nlogk) 还少的,那么就只能空间换时间了,可以用 bucket sort
    时间复杂度 O(n) 空间复杂度 也是 O(n)
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