c++手动和STL实现堆排序

来源：互联网发布：windows监控进程流量编辑：程序博客网时间：2024/05/19 09:47

好久没看最小堆了，突然上手写半天还反应不过来。手动写一下，顺便贴上代码：

手动实现：

#include<iostream>using namespace std;const int MAXN = 1000;template<typename T>class minHeap{private:intsize;Tdata[MAXN + 1];voidshiftDown(int pos);voidshiftUp(int pos);public:minHeap();voidmakeHeap(T* items, int num);voidadd(T item);Tpop();intgetSize();boolempty();voidclear();};template<typename T>minHeap<T>::minHeap(){size = 0;}template<typename T>void minHeap<T>::makeHeap(T* items, int num){clear();//不断插入构建最小堆for(int i = 0; i < num; ++i)add(items[i]);clear();//从第一个非叶节点开始调整堆size = num;for(int i = 1; i <= num; ++i)data[i] = items[i - 1];for(int i = size>>1; i> 0; --i)shiftDown(i);}template<typename T>void minHeap<T>::shiftDown(int pos){if(pos<<1 > size)return;int left = pos<<1;int right = left + 1;int minPos = left;if(right <= size && data[right] < data[left])minPos = right;if(data[minPos] < data[pos]){swap(data[minPos], data[pos]);shiftDown(minPos);}}template<typename T>void minHeap<T>::shiftUp(int pos){if(pos <= 0)return;int parent = pos>>1;if(data[pos] < data[parent]){swap(data[pos], data[parent]);shiftUp(parent);}}template<typename T>void minHeap<T>::add(T item){if(size == MAXN){cout<<"Failed to add "<<item<<" ! The heap is full!"<<endl;return;}data[++size] = item;shiftUp(size);}template<typename T>T minHeap<T>::pop(){if(size == 0){cout<<"Failed to pop the heap! The heap is empty!"<<endl;return NULL;}T t = data[1];data[1] = data[size--];shiftDown(1);return t;}template<typename T>int minHeap<T>::getSize(){return size;}template<typename T>bool minHeap<T>::empty(){return (size > 0);}template<typename T>void minHeap<T>::clear(){size = 0;}int main(){//freopen("input.txt","r",stdin);//freopen("output.txt","w",stdout);minHeap<int> heap;int m;int items[10];cin>>m;for(int i = 0; i < m; ++i){cin>>items[i];//heap.add(items[i]);}heap.makeHeap(items, 10);cout<<"heap size is "<<heap.getSize()<<endl;for(int i = 0; i < m; ++i){int item = heap.pop();cout<<item<<" ";}cout<<endl;return 0;}

STL实现：

建堆：make_heap(_First, _Last, _Comp)
默认是建立最大堆的。对int类型，可以在第三个参数传入greater<int>()得到最小堆。

在堆中添加数据：push_heap (_First, _Last)
要先在容器中加入数据，再调用push_heap ()

在堆中删除数据：pop_heap(_First, _Last)
要先调用pop_heap()再在容器中删除数据

堆排序：sort_heap(_First, _Last)
排序之后就不再是一个合法的heap了

注意：sort_heap 第三个参数必须和堆结构对应，否则会出现错误！！比如为最小堆时，sort_heap参数必须为greater<int>()，得到的排序为从大到小；为最大堆时，参数缺省或者为less<int>()，得到的排序为从小到大。这是因为sort_heap实际就是一直在做pop，把堆顶的元素交换到最后。

#include<iostream>#include<algorithm>#include<functional>#include<vector>using namespace std;void printItem(vector<int> items){for(vector<int>::iterator it = items.begin(); it != items.end(); ++it)cout<<*it<<" ";cout<<endl;}int main(){//freopen("input.txt","r",stdin);//freopen("output.txt","w",stdout);int numbers[] = {5,6,22,33,4,1,7,12,8,13};vector<int> items(numbers, numbers + 10);cout<<"---------make heap-----------"<<endl;make_heap(items.begin(), items.end(), greater<int>());//第三个参数缺省或者是less<int>()时 为最大堆printItem(items);cout<<"---------push heap-----------"<<endl;items.push_back(0);push_heap(items.begin(), items.end(), greater<int>());printItem(items);cout<<"---------pop heap-----------"<<endl;pop_heap(items.begin(), items.end(), greater<int>());items.pop_back();printItem(items);cout<<"---------sort heap-----------"<<endl;sort_heap(items.begin(), items.end(), greater<int>());printItem(items);return 0;}

0 0