Algorithm to compute mode

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孤独总比滥情好 2021-01-12 04:42

I\'m trying to devise an algorithm in the form of a function that accepts two parameters, an array and the size of the array. I want it to return the mode of the array and i

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被撕碎了的回忆 (楼主)

2021-01-12 05:25

Even though you have some good answers already, I decided to post another. I'm not sure it really adds a lot that's new, but I'm not at all sure it doesn't either. If nothing else, I'm pretty sure it uses more standard headers than any of the other answers. :-)

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main() {
    std::vector inputs{ 1, 1, 1, 1, 2, 2, 2 };

    std::unordered_map counts;
    for (int i : inputs)
        ++counts[i];

    std::multimap > inv;
    for (auto p : counts)
        inv.insert(std::make_pair(p.second, p.first));

    auto e = inv.upper_bound(inv.begin()->first);

    double sum = std::accumulate(inv.begin(),
        e,
        0.0,
        [](double a, std::pair const &b) {return a + b.second; });

    std::cout << sum / std::distance(inv.begin(), e);
}

Compared to @Dietmar's answer, this should be faster if you have a lot of repetition in the numbers, but his will probably be faster if the numbers are mostly unique.

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