CODEWITHSUNDEEP
c++qtqt4qmap
amiref
amiref

Reputation: 3431

Remove 5 first elements of QMap

How can I remove 5 first elements of a QMap?

Upvotes: 0

Views: 3111

Answers (2)

Evan Teran
Evan Teran

Reputation: 90442

Something like this would probably work:

const size_t count = std::min<size_t>(5, m.size());
for(int i = 0; i < count; ++i) {
    m.erase(m.begin());
}

DEMO:

#include <iostream>
#include <map>
#include <algorithm>

int main() {

    std::map<int,int> m;
    m.insert(std::make_pair(0,0));
    m.insert(std::make_pair(1,1));
    m.insert(std::make_pair(2,2));
    m.insert(std::make_pair(3,3));
    m.insert(std::make_pair(4,4));
    m.insert(std::make_pair(5,5));
    m.insert(std::make_pair(6,6));

    const size_t count = std::min<size_t>(5, m.size());
    for(size_t i = 0; i < count; ++i) {
        m.erase(m.begin());
    }

    for(std::map<int,int>::const_iterator it = m.begin(); it != m.end(); ++it) {
        std::cout << it->second << std::endl;
    }
}

DEMO using QMap

#include <iostream>
#include <QMap>

int main() {

    QMap<int,int> m;
    m[0] = 0;
    m[1] = 1;
    m[2] = 2;
    m[3] = 3;
    m[4] = 4;
    m[5] = 5;
    m[6] = 6;

    const size_t count = qMin<size_t>(5, m.size());
    for(size_t i = 0; i < count; ++i) {
        m.erase(m.begin());
    }

    for(QMap<int,int>::const_iterator it = m.begin(); it != m.end(); ++it) {
        std::cout << it.value() << std::endl;
    }
}

Upvotes: 3

snoofkin
snoofkin

Reputation: 8895

There is no such thing as 'First' and 'Last' in Maps. its QMap<Key, T> while elements are accessed by the Key part, which is usually non-numeric.

Upvotes: 0

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