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Populate a vector with all multimap values with a given key

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伪装坚强ぢ
伪装坚强ぢ 2021-02-08 13:10

Given a multimap M what\'s a neat way to create a vector of all values in M with a specific key.

e.g given a multimap how c

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  • 夕颜
    夕颜 (楼主)
    2021-02-08 13:43

    You need a loop anyway. All "loop-free" methods just abstract the loop away.

    #include 
#include 
#include 
#include 
using namespace std;

int main () {
    multimap mm;
    mm.insert(make_pair(1, 2.2));
    mm.insert(make_pair(4, 2.6));
    mm.insert(make_pair(1, 9.1));
    mm.insert(make_pair(1, 3.1));

    vector v;
    transform(mm.lower_bound(1), mm.upper_bound(1),
              back_inserter(v), __gnu_cxx::select2nd >());
    // note: select2nd is an SGI extension.

    for (vector::const_iterator cit = v.begin(); cit != v.end(); ++ cit)
        printf("%g, ", *cit);   // verify that you've got 2.2, 9.1, 3.1
    return 0;
}

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