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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