查找给定数字组中的数字的频率 [英] Finding Frequency of numbers in a given group of numbers

问题描述

假设我们有一个C ++中的向量/数组，我们希望计算这些N个元素中的哪一个具有最大重复出现次数，并输出最高计数。

示例：

  int a = {2，456，34，3456，2，435，2，456，2} 
  

输出为4，因为2发生4次。

解决方案

排序数组，然后快速通过计数每个数字。该算法具有O（N * logN）复杂性。

或者，使用数字作为键来创建哈希表。在哈希表中存储你键入的每个元素的计数器。你可以在一个通过计数所有元素;然而，算法的复杂性现在取决于您的hasing函数的复杂性。

Suppose we have a vector/array in C++ and we wish to count which of these N elements has maximum repetitive occurrences and output the highest count. Which algorithm is best suited for this job.

example:

int a = { 2, 456, 34, 3456, 2, 435, 2, 456, 2}

the output is 4 because 2 occurs 4 times. That is the maximum number of times 2 occurs.

解决方案

Sort the array and then do a quick pass to count each number. The algorithm has O(N*logN) complexity.

Alternatively, create a hash table, using the number as the key. Store in the hashtable a counter for each element you've keyed. You'll be able to count all elements in one pass; however, the complexity of the algorithm now depends on the complexity of your hasing function.

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