打印包含 multimap 的双端队列

Question

我需要打印一个包含多图的 dequeu，但它不起作用，我做错了什么？

int main()
{
    deque<multimap<string,int> > q_map;
    multimap<string,int> m;

    m.insert(pair<string, int>("a", 1));
    m.insert(pair<string, int>("c", 2));
    m.insert(pair<string, int>("b", 3));
    m.insert(pair<string, int>("b", 4));
    m.insert(pair<string, int>("a", 5));
    m.insert(pair<string, int>("b", 6));
    cout << "Map size: " << m.size() << endl;

    q_map.push_back(m);
    for (std::deque<int>::iterator it = q_map.begin(); it!=q_map.end(); ++it)
        std::cout << ' ' << *it;
}

我总是遇到编译器错误：

error: conversion from ‘std::_Deque_iterator<std::multimap<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int> > >, std::multimap<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int> > >&, std::multimap<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int> > >*>’ to non-scalar type ‘std::_Deque_iterator<int, int&, int*>’ requested
q_map.cpp:23: error: no match for ‘operator!=’ in ‘it != std::deque<_Tp, _Alloc>::end() [with _Tp = std::multimap<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int> > >, _Alloc = std::allocator<std::multimap<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int> > > >]()’

Answer 1

嗯，两个简单的 for 循环，一个遍历 deque，另一个遍历 multimap:

for ( auto it = q_map.begin(); it != q_map.end(); ++it )
    for ( auto it2 = (*it).begin(); it2 != (*it).end(); ++it2 )
        cout << ' ' << it2->first << ' ' << it2->second << endl;

或使用范围循环

for ( auto& it : q_map )
    for ( auto& it2 : it )
        cout << ' ' << it2.first << ' ' << it2.second << endl;

Answer 2

你属于这种类型：

deque<multimap<string,int> > q_map;

但是您正在尝试使用此类型对其进行迭代：

for (std::deque<int>::iterator it = q_map.begin(); ...

那就是你做错了。

如果您不能使用 C++11 基于范围的 for 循环或 C++11 auto 功能，那么不要重复类型 multimap<string,int>在任何地方，你都可以为它使用 typedef:

typedef multimap<string,int> mmap;

现在您可以在任何地方引用 std::deque<mmap>，因此 for 循环将使用 std::deque<mmap>::iterator

打印包含 multimap 的双端队列

print deque containing multimap

c++

multimap

deque