C ++列表迭代器算术？ [英] C++ list iterator arithmetic?

问题描述

我正在尝试使用迭代器创建一组循环，并且我遇到了一些迭代器算法（我认为可行但不起作用）。

I'm trying to create a set of loops with iterators and I'm having trouble with some iterator arithmetic (that I thought was possible but is not working).

下面是一些代码：

  for (list<Term>::iterator itr = final.begin(); itr != final.end(); itr++) {
        for(list<Term>::iterator j = itr + 1; j != final.end(); j++) {
            cout << itr->term << " " << j->term;
            if(itr->term == j->term) {
                //Do stuff
            }
        }
    }

我要做的是让j从队列中的下一个位置开始。原因是我不想检查第一个项目。错误本身来自代码中我指定 itr + 1 的部分。现在我确定用指针可以像这样做算法，为什么它不能与列表迭代器一起使用（基本上是同样的东西？）

What I am trying to do is have j start at the next place in the queue along from itr. The reason for this is I don't want to check the first item against itself. The error itself comes from the part in the code where I have specified itr + 1. Now I was sure with pointers you could do arithmetic like this, why is it not working with the list iterator (which is essentially the same thing?)

错误我是从我的IDE获取如下： main.cpp：237：48：错误：'itr + 1'中的'operator +'不匹配。我再次认为你可以在迭代器上做这种算法，所以我不确定该怎样做才能使这个工作，我可以尝试一种替代实现吗？

The error I am getting from my IDE is as follows: main.cpp:237:48: error: no match for ‘operator+’ in ‘itr + 1’. Again I thought you could do this sort of arithmetic on iterators so I'm not really sure what to do to make this work, is there an alternate implementation I could try?

推荐答案

list 具有双向迭代器，不支持 operator + 。您可以在C ++ 11中使用 std :: advance 或 std :: next 。

list has bidirectional iterators, that doesn't support operator +. You can use std::advance, or std::next in C++11.

for (list<Term>::iterator j = next(itr); j != final.end(); ++j)

或

list<Term>::iterator j = itr;
advance(j, 1); // or ++j
for (; j != final.end(); ++j)

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