c++ - 如何遍历包含 deque 元素的斐波那契堆( boost )

Question

我正在使用 Fibonacci heap(boost) 对元素数组进行排序，但我无法遍历堆。代码是这样的:

#include <deque>
#include <boost/heap/fibonacci_heap.hpp>
#include <iostream>

struct MyData {
     ...
     long int id;

     ...
}; 

struct MyCompare{
    bool operator()(const deque<MyData> &a, const deque<MyData> &b) const
    {
        return a[a.size()-1].id > b[b.size()-1].id;
    }
};


int main()
{   deque<MyData> array1;
    deque<MyData> array2;

    MyData app;
    app.id=15;
    array1.push_front(app);
    app.id=10;
    array1.push_front(app);

    app.id=5;
    array2.push_front(app);
    app.id=2;
    array2.push_front(app);

    boost::heap::fibonacci_heap<deque<MyData>, boost::heap::compare<MyCompare> > fib_heap;  
    fib_heap.push(array1);
    fib_heap.push(array2);
    boost::heap::fibonacci_heap<deque<MyData>, boost::heap::compare<MyCompare> >::iterator it;
    boost::heap::fibonacci_heap<deque<MyData>, boost::heap::compare<MyCompare> >::iterator beg =fib_heap.begin();
    boost::heap::fibonacci_heap<deque<MyData>, boost::heap::compare<MyCompare> >::iterator end =fib_heap.end();

    for (it=beg;it!=end; ++it) {
        deque<MyData> elem;
        elem =*it;
        for (int k=0;k < elem.size();k++)
            cout<<" "<<elem[k].id;
        cout<<"\n";         
    }


}

它在“elem = *it”这一行给我这个错误:recursive_tree_iterator 的实例化错误: 递归树迭代器(无效): 适配器类型(0) {}

有什么办法吗？或者使用另一个有序堆而不是 Fibonacci？非常感谢。

Answer 1

我认为错误是您不能默认构造迭代器。尝试消除 it 变量的创建并将其移动到 for 循环中:

boost::heap::fibonacci_heap<deque<MyData>, boost::heap::compare<MyCompare> >::iterator beg =fib_heap.begin();
boost::heap::fibonacci_heap<deque<MyData>, boost::heap::compare<MyCompare> >::iterator end =fib_heap.end();

for (boost::heap::fibonacci_heap<deque<MyData>, boost::heap::compare<MyCompare> >::iterator it=beg;it!=end; ++it) {
    deque<MyData> elem;
    elem =*it;
    for (size_t k=0;k < elem.size();k++)
        cout<<" "<<elem[k].id;
    cout<<"\n";         
}

为了按堆顺序迭代，你可以使用:

ordered_iterator ordered_begin(void) const;
ordered_iterator ordered_end(void) const;

此外，我认为使用 auto 关键字会对代码有益:

for (auto it=fib_heap.begin(), end=fib_heap.end();it!=end; ++it) {
    deque<MyData> elem;
    elem =*it;
    for (size_t k=0;k < elem.size();k++)
        cout<<" "<<elem[k].id;
    cout<<"\n";         
}