如何copy_if从地图到矢量? [英] How to copy_if from map to vector?
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问题描述
我想将与地图< string,int>
中的谓词(等于int)匹配的值复制到向量< int> ;
。
这是我尝试的:
#include< map> ;
#include< vector>
#include< algorithm>
int main()
{
std :: vector< int> v;
std :: map< std :: string,int> m;
m [1] = 1;
m [2] = 2;
m [3] = 3;
m [4] = 4;
m [5] = 5;
std :: copy_if(m.begin(),m.end(),v.begin(),
[](const std :: pair& & it)
{
return(0 ==(it.second%2));
}
);
}
来自g ++ 4.6.1的错误消息是:
错误:无法将转换中的'std :: pair< const std :: basic_string< char>,int>'转换为'int'有没有办法调整示例来做上面的复制? =h2_lin>解决方案使用 boost :: range
它很容易:
boost :: push_back(
v,
m | boost :: adapters :: map_values
| boost :: adapters :: filtered int val){return 0 ==(val%2);}));
I'd like to copy values that match a predicate (equal ints) from a map<string,int>
to a vector<int>
.
This is what I tried:
#include <map>
#include <vector>
#include <algorithm>
int main()
{
std::vector< int > v;
std::map< std::string, int > m;
m[ "1" ] = 1;
m[ "2" ] = 2;
m[ "3" ] = 3;
m[ "4" ] = 4;
m[ "5" ] = 5;
std::copy_if( m.begin(), m.end(), v.begin(),
[] ( const std::pair< std::string,int > &it )
{
return ( 0 == ( it.second % 2 ) );
}
);
}
The error message from g++ 4.6.1 is :
error: cannot convert 'std::pair<const std::basic_string<char>, int>' to 'int' in assignment
Is there a way to adjust the example to do the above copy?
解决方案 With boost::range
it is as easy as:
boost::push_back(
v,
m | boost::adaptors::map_values
| boost::adaptors::filtered([](int val){ return 0 == (val % 2); }));
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