blocks|key|1596474|text|如果您使用的是std::map，那么它已经按照键进行了排序。只需创建一个迭代器并遍历从begin()到end()的map，就完成了。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1596475|如果您希望按map键以外的其他元素进行排序，则可以使用相同的迭代器，并在迭代map时将每个元素的副本推送到向量上。|1596476|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

If you're using a std::map, it's already sorted by the key. Just create an iterator and iterate over the map from begin() to end() and you're done.

If you'd like to sort by something other than the map key, you can use the same iterator and push a copy of each element onto your vector as you iterate over the map.

blocks|key|1381460|text|vector<pair<K,V>+>+v(m.begin(),+m.end());|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1381461|或|unstyled|1381462|vector<pair<K,V>+>+v(m.size());
copy(m.begin(),+m.end(),+v.begin());|1381463|copy()在<algorithm>中。|offset|length|style|CODE|1381464|entityMap^0|0|0|0|0|6|7|B|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|R|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|I|3|J|5|F|7|T|8|@$K|U|L|V|M|N]|$K|W|L|X|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|F|7|Y|8|@]|9|@]|A|$]]]|P|$]]

<pre><code>vector&lt;pair&lt;K,V&gt; &gt; v(m.begin(), m.end());
</code></pre>

or

<pre><code>vector&lt;pair&lt;K,V&gt; &gt; v(m.size());
copy(m.begin(), m.end(), v.begin());
</code></pre>

<code>copy()</code> is in <code>&lt;algorithm&gt;</code>.

blocks|key|1381499|text|假设您想要复制键和值：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1381500|std::map<Foo,+Bar>+m;


//+Map+gets+populated+
//+(...)


//+Copying+it+to+a+new+vector+via+the+constructor
std::vector<std::pair<Foo,+Bar>>+v(m.begin(),+m.end());


//+Copying+it+to+an+existing+vector,+erasing+the+contents
v.assign(m.begin(),+m.end());

//+Copying+it+to+the+back+of+an+existing+vector
v.insert(v.end(),+m.begin(),+m.end());|code-block|syntax|javascript|1381501|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Assuming you want to copy the key and the value:

<pre><code>std::map&lt;Foo, Bar&gt; m;


// Map gets populated 
// (...)


// Copying it to a new vector via the constructor
std::vector&lt;std::pair&lt;Foo, Bar&gt;&gt; v(m.begin(), m.end());


// Copying it to an existing vector, erasing the contents
v.assign(m.begin(), m.end());

// Copying it to the back of an existing vector
v.insert(v.end(), m.begin(), m.end());
</code></pre>

blocks|key|1381523|text|这应该是您想要的结果：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1381524|#include+<iostream>
#include+<vector>
#include+<map>
#include+<algorithm>
#include+<iterator>

using+namespace+std;

bool+cmp(const+pair<int,+int>++&p1,+const+pair<int,+int>+&p2)
{
++++return+p1.second+<+p2.second;
}

int+main()
{
++++map<int,+int>+m;
++++for(int+i+=+0;+i+<+10;+%2B%2Bi)
++++++++m[i]+=+i+*+-i;

++++vector<pair<int,+int>+>+v;
++++copy(m.begin(),+m.end(),+back_inserter(v));

++++sort(v.begin(),+v.end(),+cmp);

++++for(int+i+=+0;+i+<+v.size();+%2B%2Bi)
++++++++cout+<<+v[i].first+<<+"+:+"+<<+v[i].second+<<+endl;
++++return+0;
}|code-block|syntax|javascript|1381525|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This should do what you want:

<pre><code>#include &lt;iostream&gt;
#include &lt;vector&gt;
#include &lt;map&gt;
#include &lt;algorithm&gt;
#include &lt;iterator&gt;

using namespace std;

bool cmp(const pair&lt;int, int&gt; &amp;p1, const pair&lt;int, int&gt; &amp;p2)
{
 return p1.second &lt; p2.second;
}

int main()
{
 map&lt;int, int&gt; m;
 for(int i = 0; i &lt; 10; ++i)
 m[i] = i * -i;

 vector&lt;pair&lt;int, int&gt; &gt; v;
 copy(m.begin(), m.end(), back_inserter(v));

 sort(v.begin(), v.end(), cmp);

 for(int i = 0; i &lt; v.size(); ++i)
 cout &lt;&lt; v[i].first &lt;&lt; " : " &lt;&lt; v[i].second &lt;&lt; endl;
 return 0;
}
</code></pre>

blocks|key|1596596|text|如果您的目的只是根据类型而不是键进行排序，那么您可能需要查看Boost::Bimap。它允许您以键的形式访问映射对的两个部分。大概你可以按照第二个键的顺序迭代它，就像第一个键一样简单。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1596597|entityMap|0|LINK|mutability|MUTABLE|url|http://www.boost.org/doc/libs/1_38_0/libs/bimap/doc/html/index.html^0|U|C|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

If your purpose is just to sort by the type instead of the key, you might want to look at <a href="http://www.boost.org/doc/libs/1_38_0/libs/bimap/doc/html/index.html" rel="nofollow noreferrer">Boost::Bimap</a>. It lets you access both parts of the map pair as keys. Presumably you could iterate over it in order of the second key just as easily as the first.

blocks|key|1596668|text|您可以使用不同的映射(或集)，并在插入时使用transform进行排序：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1596669|#include+<map>
#include+<algorithm>

typedef+std::map<unsigned+int,+signed+char>+MapType1;
typedef+std::map<MapType1::mapped_type,+MapType1::key_type>+MapType2;

struct+SwapPair
{
++MapType2::value_type+operator()(MapType1::value_type+const+&+v)
++{
++++return+std::make_pair+(v.second,+v.first);
++}
};

int+main+()
{
++MapType1+m1;
++for(int+i+=+0;+i+<+10;+%2B%2Bi)
++++m1[i]+=+i+*+-i;

++MapType2+m2;
++std::transform+(m1.begin+()
++++++,+m1.end+()
++++++,+std::inserter+(m2,+m2.end+())
++++++,+SwapPair+());
}|code-block|syntax|javascript|1596670|我忘了补充说，如果你经常需要这样做，那么使用boost+multi-index容器可能会更好。|offset|length|1596671|entityMap|0|LINK|mutability|MUTABLE|url|http://www.boost.org/doc/libs/1_38_0/libs/multi_index/doc/index.html^0|0|0|S|B|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

You can use a different map (or set) and use transform to do the sorting as you insert:

<pre><code>#include &lt;map&gt;
#include &lt;algorithm&gt;

typedef std::map&lt;unsigned int, signed char&gt; MapType1;
typedef std::map&lt;MapType1::mapped_type, MapType1::key_type&gt; MapType2;

struct SwapPair
{
 MapType2::value_type operator()(MapType1::value_type const &amp; v)
 {
 return std::make_pair (v.second, v.first);
 }
};

int main ()
{
 MapType1 m1;
 for(int i = 0; i &lt; 10; ++i)
 m1[i] = i * -i;

 MapType2 m2;
 std::transform (m1.begin ()
 , m1.end ()
 , std::inserter (m2, m2.end ())
 , SwapPair ());
}
</code></pre>

I forgot to add that if you need to do this a lot then it might be better just to use a boost <a href="http://www.boost.org/doc/libs/1_38_0/libs/multi_index/doc/index.html" rel="nofollow noreferrer">multi-index</a> container.

What's the best way in C++ to copy a pair from a map to vector? I'm doing this so I can subsequently sort the vector.

C++ how to copy a map to a vector

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