STL源碼剖析 容器 stl_queue.h

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queue

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stack 是一種配接器(adapter)，以某種容器作為底部結構，改變其介面，使之符合"先進先出"的特性。
SGI STL 預設以 deque 為 stack 底部結構
沒有遍曆行為，沒有遍曆器


樣本：

#include <queue>#include <list>#include <iostream>#include <algorithm>using namespace std;int main(){queue<int, list<int> >iqueue;iqueue.push(1);iqueue.push(2);cout << iqueue.size() << endl << iqueue.front() << endl;}

源碼：

#ifndef __SGI_STL_INTERNAL_QUEUE_H#define __SGI_STL_INTERNAL_QUEUE_H__STL_BEGIN_NAMESPACE#ifndef __STL_LIMITED_DEFAULT_TEMPLATEStemplate <class T, class Sequence = deque<T> >//預設以 deque 為底層容器#elsetemplate <class T, class Sequence>#endifclass queue {  friend bool operator== __STL_NULL_TMPL_ARGS (const queue& x, const queue& y);  friend bool operator< __STL_NULL_TMPL_ARGS (const queue& x, const queue& y);public:  typedef typename Sequence::value_type value_type;  typedef typename Sequence::size_type size_type;  typedef typename Sequence::reference reference;  typedef typename Sequence::const_reference const_reference;protected:  Sequence c;//底層容器public:  //以下完全利用 Sequence c 的操作完成 queue 的操作  bool empty() const { return c.empty(); }  size_type size() const { return c.size(); }  reference front() { return c.front(); }  const_reference front() const { return c.front(); }  reference back() { return c.back(); }  const_reference back() const { return c.back(); }  //修改介面使符合 queue "前進先出"的條件  void push(const value_type& x) { c.push_back(x); }  void pop() { c.pop_front(); }};template <class T, class Sequence>bool operator==(const queue<T, Sequence>& x, const queue<T, Sequence>& y) {  return x.c == y.c;}template <class T, class Sequence>bool operator<(const queue<T, Sequence>& x, const queue<T, Sequence>& y) {  return x.c < y.c;}

priority_queue
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priority_queue 是一個 queue ，所以只允許在底端加入元素，並從頂端取出元素，
priority_queue 帶有權值觀念，其內的元素並非依照被推入的次序排列，而是自動依照元素的權值排列。
priority_queue 以底部容器為依據，再加上 heap 處理規則，預設是以 vector 為底層容器


樣本：

int main(){int ia[] = {0,1,2,3,4,8,9,3,5};priority_queue<int> ipq(ia, ia + 9);while(!ipq.empty()){cout << ipq.top() << ' ';ipq.pop();}cout << endl;}

源碼：

#ifndef __STL_LIMITED_DEFAULT_TEMPLATEStemplate <class T, class Sequence = vector<T>, //底部預設採用 vector 容器          class Compare = less<typename Sequence::value_type> > //預設權值大的排在前面#elsetemplate <class T, class Sequence, class Compare>#endifclass  priority_queue {public:  typedef typename Sequence::value_type value_type;  typedef typename Sequence::size_type size_type;  typedef typename Sequence::reference reference;  typedef typename Sequence::const_reference const_reference;protected:  Sequence c; //底層容器  Compare comp; //元素大小比較標準public:  priority_queue() : c() {}  explicit priority_queue(const Compare& x) :  c(), comp(x) {}#ifdef __STL_MEMBER_TEMPLATES  template <class InputIterator>  priority_queue(InputIterator first, InputIterator last, const Compare& x)    : c(first, last), comp(x) { make_heap(c.begin(), c.end(), comp); }  template <class InputIterator>  priority_queue(InputIterator first, InputIterator last)     : c(first, last) { make_heap(c.begin(), c.end(), comp); }#else /* __STL_MEMBER_TEMPLATES */  priority_queue(const value_type* first, const value_type* last,                  const Compare& x) : c(first, last), comp(x) {    make_heap(c.begin(), c.end(), comp);  }  priority_queue(const value_type* first, const value_type* last)     : c(first, last) { make_heap(c.begin(), c.end(), comp); }#endif /* __STL_MEMBER_TEMPLATES */  bool empty() const { return c.empty(); }  size_type size() const { return c.size(); }  const_reference top() const { return c.front(); }  void push(const value_type& x) {    __STL_TRY {  //無利用底層容器的 push_back() 將新元素推入末端，再重排 heap()      c.push_back(x);       push_heap(c.begin(), c.end(), comp);    }    __STL_UNWIND(c.clear());  }  void pop() {    __STL_TRY {  //將權值最大或最小放在尾端      pop_heap(c.begin(), c.end(), comp);  //將用底層容器的 pop_back() 彈出      c.pop_back();    }    __STL_UNWIND(c.clear());  }};// no equality is provided__STL_END_NAMESPACE#endif /* __SGI_STL_INTERNAL_QUEUE_H */// Local Variables:// mode:C++// End: