priority_queue 调用 STL里面的 make_heap(), pop_heap(), push_heap() 算法
实现,也算是堆的另外一种形式。
先写一个用 STL 里面堆算法实现的与真正的STL里面的 priority_queue 用法相
似的 priority_queue, 以加深对 priority_queue 的理解
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#include <iostream>
#include <algorithm>
#include <vector>
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using namespace std;
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
class priority_queue
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
private:
vector<int> data;
public:
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
void push( int t )
{
data.push_back(t);
push_heap( data.begin(), data.end());
}
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
void pop()
{
pop_heap( data.begin(), data.end() );
data.pop_back();
}
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
int top()
{ return data.front(); }
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
int size()
{ return data.size(); }
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
bool empty()
{ return data.empty(); }
};
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
int main()
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![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
priority_queue test;
test.push( 3 );
test.push( 5 );
test.push( 2 );
test.push( 4 );
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
while( !test.empty() )
{
cout << test.top() << endl;
test.pop(); }
return 0;
}
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
STL里面的 priority_queue 写法与此相似,只是增加了模板及相关的迭代器什么的。
priority_queue 对于基本类型的使用方法相对简单。
他的模板声明带有三个参数,priority_queue<Type, Container, Functional>
Type 为数据类型, Container 为保存数据的容器,Functional 为元素比较方式。
Container 必须是用数组实现的容器,比如 vector, deque 但不能用 list.
STL里面默认用的是 vector. 比较方式默认用 operator< , 所以如果你把后面俩个
参数缺省的话,优先队列就是大顶堆,队头元素最大。
看例子
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
#include <iostream>
#include <queue>
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
using namespace std;
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
int main()
{
priority_queue<int> q;
for( int i= 0; i< 10; ++i ) q.push( rand() );
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
while( !q.empty() )
{
cout << q.top() << endl;
q.pop();
}
getchar();
return 0;
}
如果要用到小顶堆,则一般要把模板的三个参数都带进去。
STL里面定义了一个仿函数 greater<>,对于基本类型可以用这个仿函数声明小顶堆
例子:
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
#include <iostream>
#include <queue>
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
using namespace std;
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
int main()
{
priority_queue<int, vector<int>, greater<int> > q;
for( int i= 0; i< 10; ++i ) q.push( rand() );
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
while( !q.empty() )
{
cout << q.top() << endl;
q.pop();
}
getchar();
return 0;
}
对于自定义类型,则必须自己重载 operator< 或者自己写仿函数
先看看例子:
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
#include <iostream>
#include <queue>
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
using namespace std;
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
struct Node
{
int x, y;
Node( int a= 0, int b= 0 ):
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
x(a), y(b)
{}
};
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
bool operator<( Node a, Node b )
{
if( a.x== b.x ) return a.y> b.y;
return a.x> b.x;
}
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
int main()
{
priority_queue<Node> q;
for( int i= 0; i< 10; ++i )
q.push( Node( rand(), rand() ) );
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
while( !q.empty() )
{
cout << q.top().x << ' ' << q.top().y << endl;
q.pop();
}
getchar();
return 0;
}
自定义类型重载 operator< 后,声明对象时就可以只带一个模板参数。
但此时不能像基本类型这样声明
priority_queue<Node, vector<Node>, greater<Node> >;
原因是 greater<Node> 没有定义,如果想用这种方法定义
则可以按如下方式
例子:
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
#include <iostream>
#include <queue>
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
using namespace std;
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
struct Node
{
int x, y;
Node( int a= 0, int b= 0 ):
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
x(a), y(b)
{}
};
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
struct cmp
{
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
bool operator() ( Node a, Node b )
{
if( a.x== b.x ) return a.y> b.y;
return a.x> b.x; }
};
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
int main()
{
priority_queue<Node, vector<Node>, cmp> q;
for( int i= 0; i< 10; ++i )
q.push( Node( rand(), rand() ) );
![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
while( !q.empty() )
{
cout << q.top().x << ' ' << q.top().y << endl;
q.pop();
}
getchar();
return 0;
}
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
posted on 2009-06-09 18:00
Darren 阅读(15752)
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