C++ 如何在c ++中反向迭代地图
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/732160/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
how to iterate in reverse over a map in c++
提问by Hyman BeNimble
I'm having trouble iterating in reverse over a map in gcc c++. When I use a reverse iterator, it seems I can't assign anything to it - the compiler complains. I'm working around it with some awkward code using a forward iterator, but it's not very elegant. Any thoughts?
我在 gcc c++ 中反向迭代地图时遇到了麻烦。当我使用反向迭代器时，似乎我无法为其分配任何内容 - 编译器抱怨。我正在使用前向迭代器处理一些笨拙的代码，但它不是很优雅。有什么想法吗？
回答by GManNickG
Here's an example of iterating backward through a std::map:
这是一个通过 a 向后迭代的示例std::map：
#include <iostream>
#include <map>
#include <string>
int main() {
std::map<std::string, std::string> m;
m["a"] = "1";
m["b"] = "2";
m["c"] = "3";
for (auto iter = m.rbegin(); iter != m.rend(); ++iter) {
std::cout << iter->first << ": " << iter->second << std::endl;
}
}
If you are pre-C++11, you'll just need to spell out auto, which is:
如果您是 C++11 之前的，您只需要拼出auto，即：
std::map<std::string, std::string>::reverse_iterator
Note that if you're using boost, you can use a range-based for loop with a reverse adapter:
请注意，如果您使用的是 boost，则可以使用带有反向适配器的基于范围的 for 循环：
#include <boost/range/adaptor/reversed.hpp>
for (auto& iter : boost::adaptors::reverse(m)) {
std::cout << iter.first << ": " << iter.second << std::endl;
}
