Iterating a vector in reverse order with a range-for loop? [duplicate]

问题

This question already has answers here:

C++11 reverse range-based for-loop (9 answers)

Closed 10 months ago.

I want to iterate a vector in reverse order , i know that i can do it easily by below code

#include<bits/stdc++.h>
using namespace std;
int main()
{
    vector<int> v(10);
    for(auto it=v.rbegin();it!=v.rend();it++)
        cout<<*it<<"";
}

For iterating in forward we can simply do by below code.

for(auto it:v)
  cout<<it<<" ";

Now task is ...

Is it possible to do reverse iterate similar to for(auto it:v) cout<<it<<" ". If YES then How?

回答1:

If you can use C++20, you can use the ranges library and thus std::ranges::reverse_view:

vector<int> v(10);
std::ranges::reverse_view vReversed{v};

for(auto it : vReversed)
    cout<<it<<" ";

回答2:

Or you can write one on your own. Something like

template<class Source>
struct Reverse {
     Reverse(Source &&s): s(std::forward<Source>(s)) {}
     constexpr decltype(auto) begin() const { return std::rbegin(s); }
     constexpr decltype(auto end() const { return std::rend(s); }
private:
     S &&s;
};

来源：https://stackoverflow.com/questions/61182699/iterating-a-vector-in-reverse-order-with-a-range-for-loop