使用基于范围的 for 循环时需要迭代器

问题描述

目前，我只能用这个做基于范围的循环:

Currently, I can only do ranged based loops with this:

for (auto& value : values)

但有时我需要一个值的迭代器，而不是引用(无论出于何种原因).有没有什么方法不需要遍历整个向量比较值?

But sometimes I need an iterator to the value, instead of a reference (For whatever reason). Is there any method without having to go through the whole vector comparing values?

推荐答案

使用旧的 for 循环:

for (auto it = values.begin(); it != values.end();  ++it )
{
       auto & value = *it;
       //...
}

有了这个，你就有了 value 和迭代器 it.想用什么就用什么.

With this, you've value as well as iterator it. Use whatever you want to use.

虽然我不推荐这样做，但是如果您想使用基于范围的 for 循环(是的，无论出于何种原因 :D)，那么您可以这样做这个:

Although I wouldn't recommended this, but if you want to use range-based for loop (yeah, For whatever reason :D), then you can do this:

 auto it = std::begin(values); //std::begin is a free function in C++11
 for (auto& value : values)
 {
     //Use value or it - whatever you need!
     //...
     ++it; //at the end OR make sure you do this in each iteration
 }

这种方法避免了搜索给定的value，因为value 和it 总是同步的.

This approach avoids searching given value, since value and it are always in sync.

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