使用迭代器从STL列表中删除C ++结构

问题描述

我有这个测试程序。我不知道如何使用迭代器删除列表中的结构。

I have this test program. I don't know how to delete struct in the list using iterator.

#include<iostream>
#include<list>
using namespace std;
typedef struct Node
{
    int * array;
    int id;
}Node;

void main()
{
    list<Node> nlist;
    for(int i=0;i<3;i++)
    {
        Node * p = new Node;//how to delete is later?

        p->array = new int[5];//new array
        memset(p->array,0,5*sizeof(int));

        p->id = i;

        nlist.push_back(*p);//push node into list
    }

    //delete each struct in list
    list<Node>::iterator lt = nlist.begin();
    while( lt != nlist.end())
    {
        delete [] lt->array;

        delete &(*lt);//how to delete the "Node"?

        lt++;
    }
}

我知道如何分别删除struct。它是这样的：

I know how to delete the struct separately. It's like this:

Node * p = new Node;
p->array = new int[5];

delete [] p->array; //delete the array
delete p;//delete the struct

被推回到列表中，我不知道如何根据列表迭代器删除它。

However, when it is pushed back into list, I don't know how to delete it according to the list iterator.

list<Node>::iterator lt = nlist.begin();
while( lt != nlist.end())
{
    delete [] lt->array;

    delete &(*lt);//how to delete the "Node"?

    lt++;
}

推荐答案

list ：

nlist.push_back(*p)

它实际上是创建一个 Node $ c>并从刚刚动态分配但不使用实际指针的节点复制数据。然后您尝试从系统将自动删除的对象中删除指针：

it is actually creating a Node() and copying the data from the node you just dynamically allocated but not using the actual pointer. And then you try to delete a pointer from the object that the system will automatically delete:

delete &(*lt); // this causes double free

您需要声明列表，如 list< Node *> ，以便将指针插入列表。虽然你不应该真正处理这种在c ++中的分配，有几个修改你的代码应该工作：

You need to declare the list like list<Node*> so that the pointer is inserted into the list. Although you should not really deal with this kind of allocation in c++, with a couple of modifications your code should work:

int main()
{
  list<Node*> nlist;
  for(int i=0;i<3;i++)
  {
    Node *p = new Node;//how to delete is later?

    p->array = new int[5];//new array
    memset(p->array,0,5*sizeof(int));

    p->id = i;

    nlist.push_back(p);//push node into list
  }

  //delete each struct in list
  list<Node*>::iterator lt = nlist.begin();
  while( lt != nlist.end())
  {
    delete [] (*lt)->array;

    delete *lt;//how to delete the "Node"?

    lt++;
  }

  return 0;
}

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