概述

操作总结

异常处理

deque和vector功能上的对比，但是接口是一样的

实例

构造

std::deque::deque

#include <deque>
#include <string>
#include <iostream>
 
template<typename T>
std::ostream& operator<<(std::ostream& s, const std::deque<T>& v)
{
    s.put('[');
    char comma[3] = {'\0', ' ', '\0'};
    for (const auto& e : v) {
        s << comma << e;
        comma[0] = ',';
    }
    return s << ']';
}
 
int main() 
{
    // C++11 初始化器列表语法：
    std::deque<std::string> words1 {"the", "frogurt", "is", "also", "cursed"};
    std::cout << "words1: " << words1 << '\n';
 
    // words2 == words1
    std::deque<std::string> words2(words1.begin(), words1.end());
    std::cout << "words2: " << words2 << '\n';
 
    // words3 == words1
    std::deque<std::string> words3(words1);
    std::cout << "words3: " << words3 << '\n';
 
    // words4 为 {"Mo", "Mo", "Mo", "Mo", "Mo"}
    std::deque<std::string> words4(5, "Mo");
    std::cout << "words4: " << words4 << '\n';
}

std::deque::assign

#include <deque>
#include <iostream>
 
int main()
{
    std::deque<char> characters;
 
    characters.assign(5, 'a');
 
    for (char c : characters) {
        std::cout << c << ' ';
    } 
 
    characters.assign({'\n', 'C', '+', '+', '1', '1', '\n'});
 
    for (char c : characters) {
        std::cout << c;
    }
}

元素访问

std::deque::at

#include <iostream>
#include <deque>
 
int main()
{
    std::deque<int> data = { 1, 2, 4, 5, 5, 6 };
 
    // Set element 1
    data.at(1) = 88;
 
    // Read element 2
    std::cout << "Element at index 2 has value " << data.at(2) << '\n';
 
    std::cout << "data size = " << data.size() << '\n';
 
    try {
        // Set element 6
        data.at(6) = 666;
    } catch (std::out_of_range const& exc) {
        std::cout << exc.what() << '\n';
    }
 
    // Print final values
    std::cout << "data:";
    for (int elem : data)
        std::cout << " " << elem;
    std::cout << '\n';
}

std::deque::operator[]

返回位于指定位置 pos 的元素的引用。不进行边界检查。通过此运算符访问不存在的元素是未定义行为。

#include <deque>
#include <iostream>
 
int main()
{
    std::deque<int> numbers {2, 4, 6, 8};
 
    std::cout << "Second element: " << numbers[1] << '\n';
 
    numbers[0] = 5;
 
    std::cout << "All numbers:";
    for (auto i : numbers) {
        std::cout << ' ' << i;
    }
    std::cout << '\n';
}

std::deque::front、std::deque::back

std::deque::front

std::deque::back

#include <deque>
#include <iostream>
 
int main()
{
    std::deque<char> letters {'o', 'm', 'g', 'w', 't', 'f'};
 
    if (!letters.empty()) {
        std::cout << "The first character is: " << letters.front() << '\n';
         std::cout << "The last character is: " << letters.back() << '\n';
    }  
}

容量

std::deque::empty

#include <deque>
#include <iostream>
 
int main()
{
    std::deque<int> numbers;
    std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';
 
    numbers.push_back(42);
    numbers.push_back(13317); 
    std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
}

std::deque::size

#include <deque>
#include <iostream>
 
int main()
{ 
    std::deque<int> nums {1, 3, 5, 7};
 
    std::cout << "nums contains " << nums.size() << " elements.\n";
}

std::deque::max_size

#include <iostream>
#include <deque>
 
int main()
{
    std::deque<char> s;
    std::cout << "Maximum size of a 'deque' is " << s.max_size() << "\n";
}

std::deque::shrink_to_fit

#include <deque>
 
int main() {
    std::deque<int> nums(1000, 42);
    nums.push_front(1);
    nums.pop_front();
 
    nums.clear();
 
    // nums 现在不含项目，但它仍保有分配的内存。
    // 调用 shrink_to_fit 可能会释放任何不使用的内存。
    nums.shrink_to_fit();
}

修改器

std::deque::clear

#include <algorithm>
#include <iostream>
#include <deque>
 
int main()
{
    std::deque<int> container{1, 2, 3};
 
    auto print = [](const int& n) { std::cout << " " << n; };
 
    std::cout << "Before clear:";
    std::for_each(container.begin(), container.end(), print);
    std::cout << "\nSize=" << container.size() << '\n';
 
    std::cout << "Clear\n";
    container.clear();
 
    std::cout << "After clear:";
    std::for_each(container.begin(), container.end(), print);
    std::cout << "\nSize=" << container.size() << '\n';
}

std :: deque :: insert

作用：插入元素到指定位置

// inserting into a deque
#include <iostream>
#include <deque>
#include <vector>

int main ()
{
  std::deque<int> mydeque;

  // set some initial values:
  for (int i=1; i<6; i++) mydeque.push_back(i); // 1 2 3 4 5

  std::deque<int>::iterator it = mydeque.begin();
  ++it;

  it = mydeque.insert (it,10);                  // 1 10 2 3 4 5
  // "it" now points to the newly inserted 10

  mydeque.insert (it,2,20);                     // 1 20 20 10 2 3 4 5
  // "it" no longer valid!

  it = mydeque.begin()+2;

  std::vector<int> myvector (2,30);
  mydeque.insert (it,myvector.begin(),myvector.end());
                                                // 1 20 30 30 20 10 2 3 4 5

  std::cout << "mydeque contains:";
  for (it=mydeque.begin(); it!=mydeque.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

std :: deque :: emplace

作用：构造并插入元素到指定位置

// deque::emplace
#include <iostream>
#include <deque>

int main ()
{
  std::deque<int> mydeque = {10,20,30};

  auto it = mydeque.emplace ( mydeque.begin()+1, 100 );
  mydeque.emplace ( it, 200 );
  mydeque.emplace ( mydeque.end(), 300 );

  std::cout << "mydeque contains:";
  for (auto& x: mydeque)
    std::cout << ' ' << x;
  std::cout << '\n';

  return 0;
}

#include <iostream>
#include <string>
#include <deque>
 
struct A {
    std::string s;
    A(std::string str) : s(std::move(str))  { std::cout << " constructed\n"; }
    A(const A& o) : s(o.s) { std::cout << " copy constructed\n"; }
    A(A&& o) : s(std::move(o.s)) { std::cout << " move constructed\n"; }
    A& operator=(const A& other) {
        s = other.s;
        std::cout << " copy assigned\n";
        return *this;
    }
    A& operator=(A&& other) {
        s = std::move(other.s);
        std::cout << " move assigned\n";
        return *this;
    }
};
 
int main()
{
    std::deque<A> container;
 
    std::cout << "construct 2 times A:\n";
    A two { "two" };
    A three { "three" };
 
    std::cout << "emplace:\n";
    container.emplace(container.end(), "one");
 
    std::cout << "emplace with A&:\n";
    container.emplace(container.end(), two);
 
    std::cout << "emplace with A&&:\n";
    container.emplace(container.end(), std::move(three));
 
    std::cout << "content:\n";
    for (const auto& obj : container)
        std::cout << ' ' << obj.s;
    std::cout << '\n';
}

std::deque::emplace_front

在开始时构造并插入元素

// deque::emplace_from
#include <iostream>
#include <deque>

int main ()
{
  std::deque<int> mydeque = {10,20,30};

  mydeque.emplace_front (111);
  mydeque.emplace_front (222);

  std::cout << "mydeque contains:";
  for (auto& x: mydeque)
    std::cout << ' ' << x;
  std::cout << '\n';

  return 0;
}

std::deque::emplace_back

// deque::emplace_from
#include <iostream>
#include <deque>

int main ()
{
  std::deque<int> mydeque = {10,20,30};

  mydeque.emplace_back (100);
  mydeque.emplace_back (200);

  std::cout << "mydeque contains:";
  for (auto& x: mydeque)
    std::cout << ' ' << x;
  std::cout << '\n';

  return 0;
}

#include <deque>
#include <string>
#include <iostream>
 
struct President
{
    std::string name;
    std::string country;
    int year;
 
    President(std::string p_name, std::string p_country, int p_year)
        : name(std::move(p_name)), country(std::move(p_country)), year(p_year)
    {
        std::cout << "I am being constructed.\n";
    }
    President(President&& other)
        : name(std::move(other.name)), country(std::move(other.country)), year(other.year)
    {
        std::cout << "I am being moved.\n";
    }
    President& operator=(const President& other) = default;
};
 
int main()
{
    std::deque<President> elections;
    std::cout << "emplace_back:\n";
    elections.emplace_back("Nelson Mandela", "South Africa", 1994);
 
    std::deque<President> reElections;
    std::cout << "\npush_back:\n";
    reElections.push_back(President("Franklin Delano Roosevelt", "the USA", 1936));
 
    std::cout << "\nContents:\n";
    for (President const& president: elections) {
        std::cout << president.name << " was elected president of "
                  << president.country << " in " << president.year << ".\n";
    }
    for (President const& president: reElections) {
        std::cout << president.name << " was re-elected president of "
                  << president.country << " in " << president.year << ".\n";
    }
}

std::deque::push_front

void push_front（const value_type＆val）;
void push_front（value_type && val）;

在双端队列容器的当前位置的第一个元素之前插入一个新元素。val的内容被复制（或移动）到插入的元素。

// deque::push_front
#include <iostream>
#include <deque>

int main ()
{
  std::deque<int> mydeque (2,100);     // two ints with a value of 100
  mydeque.push_front (200);
  mydeque.push_front (300);

  std::cout << "mydeque contains:";
  for (std::deque<int>::iterator it = mydeque.begin(); it != mydeque.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

std::deque::push_back

#include <deque>
#include <iostream>
#include <iomanip>
 
int main()
{
    std::deque<std::string> letters;
 
    letters.push_back("abc");
    std::string s = "def";
    letters.push_back(std::move(s));
 
    std::cout << "deque holds: ";
    for (auto&& i : letters) std::cout << std::quoted(i) << ' ';
    std::cout << "\nMoved-from string holds " << std::quoted(s) << '\n';
}

std::deque::pop_front

// deque::emplace_from
#include <iostream>
#include <deque>

int main ()
{
  std::deque<int> mydeque = {10,20,30};

  mydeque.emplace_front (111);
  mydeque.emplace_front (222);

  std::cout << "mydeque contains:";
  for (auto& x: mydeque)
    std::cout << ' ' << x;
  std::cout << '\n';

  return 0;
}

std::deque::pop_back

#include <deque>
#include <iostream>
 
template<class T>
void print(T const & xs)
{
    std::cout << "[ ";
    for(auto && x : xs) {
        std::cout << x << ' ';
    }
    std::cout << "]\n";
}
 
int main()
{
    std::deque<int> numbers;
 
    print(numbers); 
 
    numbers.push_back(5);
    numbers.push_back(3);
    numbers.push_back(4);
 
    print(numbers); 
 
    numbers.pop_back();
 
    print(numbers); 
}

std::deque::erase

作用：擦除指定位置的元素

#include <deque>
#include <iostream>
 
 
int main( )
{
    std::deque<int> c{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    for (auto &i : c) {
        std::cout << i << " ";
    }
    std::cout << '\n';
 
    c.erase(c.begin());
 
    for (auto &i : c) {
        std::cout << i << " ";
    }
    std::cout << '\n';
 
    c.erase(c.begin()+2, c.begin()+5);
 
    for (auto &i : c) {
        std::cout << i << " ";
    }
    std::cout << '\n';
}

std::deque::resize

#include <iostream>
#include <deque>
int main()
{
    std::deque<int> c = {1, 2, 3};
    std::cout << "The deque holds: ";
    for(auto& el: c) std::cout << el << ' ';
    std::cout << '\n';
    c.resize(5);
    std::cout << "After resize up to 5: ";
    for(auto& el: c) std::cout << el << ' ';
    std::cout << '\n';
    c.resize(2);
    std::cout << "After resize down to 2: ";
    for(auto& el: c) std::cout << el << ' ';
    std::cout << '\n';
}

std::deque::swap

#include <iostream>
#include <deque>
 
template<class Os, class Co> Os& operator<<(Os& os, const Co& co) {
    os << "{";
    for (auto const& i : co) { os << ' ' << i; }
    return os << " } ";
}
 
int main()
{
    std::deque<int> a1{1, 2, 3}, a2{4, 5};
 
    auto it1 = std::next(a1.begin());
    auto it2 = std::next(a2.begin());
 
    int& ref1 = a1.front();
    int& ref2 = a2.front();
 
    std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
    a1.swap(a2);
    std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
 
    // 注意交换后迭代器与引用保持与其原来的元素关联，例如指向 'a1' 中值为 2 的元素的 it1 仍指向同一元素，
    // 尽管此元素被移动到 'a2' 中。
}

其他

==,!=,<,<=,>,>=,<=>

作用：按照字典顺序比较 deque 中的值

#include <iostream>
#include <deque>
 
int main()
{
    std::deque<int> alice{1, 2, 3};
    std::deque<int> bob{7, 8, 9, 10};
    std::deque<int> eve{1, 2, 3};
 
    std::cout << std::boolalpha;
 
    // 比较不相等的容器
    std::cout << "alice == bob returns " << (alice == bob) << '\n';
    std::cout << "alice != bob returns " << (alice != bob) << '\n';
    std::cout << "alice <  bob returns " << (alice < bob) << '\n';
    std::cout << "alice <= bob returns " << (alice <= bob) << '\n';
    std::cout << "alice >  bob returns " << (alice > bob) << '\n';
    std::cout << "alice >= bob returns " << (alice >= bob) << '\n';
 
    std::cout << '\n';
 
    // 比较相等的容器
    std::cout << "alice == eve returns " << (alice == eve) << '\n';
    std::cout << "alice != eve returns " << (alice != eve) << '\n';
    std::cout << "alice <  eve returns " << (alice < eve) << '\n';
    std::cout << "alice <= eve returns " << (alice <= eve) << '\n';
    std::cout << "alice >  eve returns " << (alice > eve) << '\n';
    std::cout << "alice >= eve returns " << (alice >= eve) << '\n';
}

std::swap(std::deque)

#include <algorithm>
#include <iostream>
#include <deque>
 
int main()
{
    std::deque<int> alice{1, 2, 3};
    std::deque<int> bob{7, 8, 9, 10};
 
    auto print = [](const int& n) { std::cout << " " << n; };
 
    // 打印交换前的状态
    std::cout << "alice:";
    std::for_each(alice.begin(), alice.end(), print);
    std::cout << '\n';
    std::cout << "bob  :";
    std::for_each(bob.begin(), bob.end(), print);
    std::cout << '\n';
 
    std::cout << "-- SWAP\n";
    std::swap(alice,bob);
 
    // 打印交换后的状态
    std::cout << "alice:";
    std::for_each(alice.begin(), alice.end(), print);
    std::cout << '\n';
    std::cout << "bob  :";
    std::for_each(bob.begin(), bob.end(), print);
    std::cout << '\n';
}

std::erase, std::erase_if (std::deque)

#include <iostream>
#include <numeric>
#include <deque>
 
void print_container(const std::deque<char>& c)
{
    for (auto x : c) {
        std::cout << x << ' ';
    }
    std::cout << '\n';
}
 
int main()
{
    std::deque<char> cnt(10);
    std::iota(cnt.begin(), cnt.end(), '0');
 
    std::cout << "Init:\n";
    print_container(cnt);
 
    auto erased = std::erase(cnt, '3');
    std::cout << "Erase \'3\':\n";
    print_container(cnt);
 
    std::erase_if(cnt, [](char x) { return (x - '0') % 2 == 0; });
    std::cout << "Erase all even numbers:\n";
    print_container(cnt);
    std::cout << "In all " << erased << " even numbers were erased.\n";
}