How can I iterate in reverse over a map in C++?

前端未结

关注

 2  1875

春和景丽 2021-02-06 23:14

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 aro

2条回答

北海茫月 (楼主)

2021-02-06 23:30
Since C++20 you can make use of the range adaptor std::views::reverse from the Ranges library. If you add this to a range-based for loop with structured binding, iterating backwards over an std::map could be done as follows:
```
#include 
#include 
#include 

int main() {
    std::map m = { {"a", 1}, {"b", 2}, {"c", 3} };

    for (auto const& [k, v] : m | std::views::reverse)
        std::cout << k << " => " << v << std::endl;

    return 0;
}
```
Output:

c => 3
b => 2
a => 1

Code on Wandbox
0 讨论(0)

查看其它2个回答
发布评论:

提交评论
- 加载中...