#STL：优先队列数据结构函数的用法 #堆 #优先队列数据结构（堆） #priority_queue 20.10.17

目录

• 点这里运行下面的程序
• • empty（）
  • size()
  • top()
  • push()
  • pop()
• 以下是 c++11版 才有的
• • emplace()直接加入操作
  • swap()
• 小根堆的写法（直接定义时默认是大根堆）

点这里运行下面的程序

empty（）

// priority_queue::empty
#include <iostream>       // std::cout
#include <queue>          // std::priority_queue

int main ()
{
  std::priority_queue<int> mypq;
  int sum (0);

  for (int i=1;i<=10;i++) mypq.push(i);

  while (!mypq.empty())
  {
     sum += mypq.top();
     mypq.pop();
  }

  std::cout << "total: " << sum << '
';

  return 0;
}

size()

// priority_queue::size
#include <iostream>       // std::cout
#include <queue>          // std::priority_queue

int main ()
{
  std::priority_queue<int> myints;
  std::cout << "0. size: " << myints.size() << '
';

  for (int i=0; i<5; i++) myints.push(i);
  std::cout << "1. size: " << myints.size() << '
';

  myints.pop();
  std::cout << "2. size: " << myints.size() << '
';

  return 0;
}

top()

// priority_queue::top
#include <iostream>       // std::cout
#include <queue>          // std::priority_queue

int main ()
{
  std::priority_queue<int> mypq;

  mypq.push(10);
  mypq.push(20);
  mypq.push(15);

  std::cout << "mypq.top() is now " << mypq.top() << '
';

  return 0;
}

push()

// priority_queue::push/pop
#include <iostream>       // std::cout
#include <queue>          // std::priority_queue

int main ()
{
  std::priority_queue<int> mypq;

  mypq.push(30);
  mypq.push(100);
  mypq.push(25);
  mypq.push(40);

  std::cout << "Popping out elements...";
  while (!mypq.empty())
  {
     std::cout << ' ' << mypq.top();
     mypq.pop();
  }
  std::cout << '
';

  return 0;
}

pop()

// priority_queue::push/pop
#include <iostream>       // std::cout
#include <queue>          // std::priority_queue

int main ()
{
  std::priority_queue<int> mypq;

  mypq.push(30);
  mypq.push(100);
  mypq.push(25);
  mypq.push(40);

  std::cout << "Popping out elements...";
  while (!mypq.empty())
  {
     std::cout << ' ' << mypq.top();
     mypq.pop();
  }
  std::cout << '
';

  return 0;
}

以下是 c++11版 才有的

emplace()直接加入操作

// priority_queue::emplace
#include <iostream>       // std::cout
#include <queue>          // std::priority_queue
#include <string>         // std::string

int main ()
{
  std::priority_queue<std::string> mypq;

  mypq.emplace("orange");
  mypq.emplace("strawberry");
  mypq.emplace("apple");
  mypq.emplace("pear");

  std::cout << "mypq contains:";
  while (!mypq.empty())
  {
     std::cout << ' ' << mypq.top();
     mypq.pop();
  }
  std::cout << '
';

  return 0;
}

swap()

// priority_queue::swap
#include <iostream>       // std::cout
#include <queue>          // std::priority_queue

int main ()
{
  std::priority_queue<int> foo,bar;
  foo.push (15); foo.push(30); foo.push(10);
  bar.push (101); bar.push(202);

  foo.swap(bar);

  std::cout << "size of foo: " << foo.size() << '
';
  std::cout << "size of bar: " << bar.size() << '
';

  return 0;
}

小根堆的写法（直接定义时默认是大根堆）

#include <iostream>  
#include <queue>    
using namespace std;
int main ()
{
//	这是大根堆，直接定义就好了
//  priority_queue< int> mypq;
//	这是小根堆，里面的东西我也不知道为什么这么写……
    priority_queue< int, vector<int>, greater<int> > mypq;
  mypq.push(10);
  mypq.push(20);
  mypq.push(15);

  cout << "mypq.top() is now " << mypq.top() << '
';

  return 0;
}