我想知道是否有任何技巧使用地图复制功能将地图内容复制到数组中。由于STL地图由键值和映射值组合,因此地图的元素形成键值对。这阻止了我们使用标准算法,如std :: copy。例如下面的代码提供了错误:是否可以使用地图的STL复制功能
#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
int
main()
{
std::map <int, double> test(4);
test[0] = 11;
test[2] = 1.23;
test[3] = 23.29;
test[1] = 12.12;
double *test_arr = (double *) malloc(4 * sizeof(double));
std::copy(test.begin(), test.end(), test_arr);
std::cout << test_arr[3] << std::endl;
return 0;
}
错误:
stl_copy_tests.cpp: In function ‘int main()’:
stl_copy_tests.cpp:9:32: error: no matching function for call to ‘std::map<int, double>::map(int)’
/usr/include/c++/4.5/bits/stl_map.h:170:7: note: candidates are: std::map<_Key, _Tp, _Compare, _Alloc>::map(const std::map<_Key, _Tp, _Compare, _Alloc>&) [with _Key = int, _Tp = double, _Compare = std::less<int>, _Alloc = std::allocator<std::pair<const int, double> >, std::map<_Key, _Tp, _Compare, _Alloc> = std::map<int, double>]
/usr/include/c++/4.5/bits/stl_map.h:159:7: note: std::map<_Key, _Tp, _Compare, _Alloc>::map(const _Compare&, const allocator_type&) [with _Key = int, _Tp = double, _Compare = std::less<int>, _Alloc = std::allocator<std::pair<const int, double> >, allocator_type = std::allocator<std::pair<const int, double> >]
/usr/include/c++/4.5/bits/stl_map.h:150:7: note: std::map<_Key, _Tp, _Compare, _Alloc>::map() [with _Key = int, _Tp = double, _Compare = std::less<int>, _Alloc = std::allocator<std::pair<const int, double> >]
In file included from /usr/include/c++/4.5/bits/char_traits.h:41:0,
from /usr/include/c++/4.5/ios:41,
from /usr/include/c++/4.5/ostream:40,
from /usr/include/c++/4.5/iostream:40,
from stl_copy_tests.cpp:1:
/usr/include/c++/4.5/bits/stl_algobase.h: In static member function ‘static _OI std::__copy_move<<anonymous>, <anonymous>, <template-parameter-1-3> >::__copy_m(_II, _II, _OI) [with _II = std::_Rb_tree_iterator<std::pair<const int, double> >, _OI = double*, bool <anonymous> = false, bool <anonymous> = false, <template-parameter-1-3> = std::bidirectional_iterator_tag]’:
/usr/include/c++/4.5/bits/stl_algobase.h:404:70: instantiated from ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false, _II = std::_Rb_tree_iterator<std::pair<const int, double> >, _OI = double*]’
/usr/include/c++/4.5/bits/stl_algobase.h:442:39: instantiated from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = false, _II = std::_Rb_tree_iterator<std::pair<const int, double> >, _OI = double*]’
/usr/include/c++/4.5/bits/stl_algobase.h:474:18: instantiated from ‘_OI std::copy(_II, _II, _OI) [with _II = std::_Rb_tree_iterator<std::pair<const int, double> >, _OI = double*]’
stl_copy_tests.cpp:15:47: instantiated from here
/usr/include/c++/4.5/bits/stl_algobase.h:319:6: error: cannot convert ‘std::pair<const int, double>’ to ‘double’ in assignment
有没有简单的把戏/黑客来克服这个问题。
声明:对在for循环中迭代映射的解决方案不感兴趣,并向元素添加元素。除非,是的,你自己把它打开
在您免责声明:你到底是什么做你认为'std :: copy'呢? – Xeo 2011-06-01 11:10:42
@Xeo:他意味着他不想在他的代码中写出循环。 – 2011-06-01 11:11:49
重度相关:http://stackoverflow.com/questions/771453/copy-map-values-to-vector-in-stl – 2011-06-01 11:12:41