Chapter 8.顺序容器deque

deque简介

deque被实现为双端队列，由多个连续内存块构成，deque是list和vector的兼容，分为多个块，每一个块大小是512字节，块通过map块管理，map块里保存每个块得首地址。因此该容器也有索引操作operator[ ]，效率没vector高。，同样的也可以通过[]、at()来随机访问元素，所以在实现上面deque不保证在内存中以严格的连续地址存放，所以实现上面比vector要复杂的多

deque的优点

1.可以通过[]/at()来实现随机访问元素

2.可以通过迭代器以多种顺序来遍历各元素

3.可以高效的通过push_front()/pop_front/push_back()/pop_back()在其队头或队尾添加或移除元素

Capacity:

emptyTest whether deque is emptysizeReturn sizemax_sizeReturn maximum size [test winxp 32bit vs2008 value is: 1073741823]resizeChange size

Element access:

operator[]Access elementatAccess elementfrontAccess first elementbackAccess last element

Modifiers:

assignAssign list contentpush_backAdd element at the endpop_backDelete last elementinsertInsert elementseraseErase elementsswapSwap content//algorithm exists swap, and the same behavior.clearClear contentpush_frontInsert element at beginning→list and deque uniquepop_frontDelete first element→list and deque unique

Allocator:

get_allocator

eg:  deque<int> mydeque;  int * p;  unsigned int i;  // allocate an array of 5 elements using deque's allocator:  p=mydeque.get_allocator().allocate(5);  // assign some values to array  for (i=0; i<5; i++) p[i]=i;  cout << "The allocated array contains:";  for (i=0; i<5; i++) cout << " " << p[i];  cout << endl;  mydeque.get_allocator().deallocate(p,5);

Output:

The allocated array contains: 0 1 2 3 4