我正在编写一个创建具有对象ID和优先级的maxheap的项目 优先级是要比较的int。 对象ID可以是int，char或string。
我在堆中创建了一个必需的比较函数。
class pairpairCompare {
public:
static bool lt(pair<int,int> x, pair<int,int> y) { return x.second < y.second; }
static bool eq(pair<int,int> x, pair<int,int> y) { return x.second == y.second; }
static bool gt(pair<int,int> x, pair<int,int> y) { return x.second > y.second; }
};
它适用于pair<int, int>* pairArr=new pair<int, int>[maxArrayRoom];
致电
maxheap<pair<int, int>,pairpairCompare> PairTtest(pairArr,0,maxArrayRoom);
现在我想要更新，以便pair<char, int>* pairArr=new pair<int, int>[maxArrayRoom];或pair<string, int>* pairArr=new pair<int, int>[maxArrayRoom];可以正常工作
我试过了。
template <class Elem>
class pairpairCompare {
public:
static bool lt(pair<Elem,int> x, pair<Elem,int> y) { return x.second < y.second; }
static bool eq(pair<Elem,int> x, pair<Elem,int> y) { return x.second == y.second; }
static bool gt(pair<Elem,int> x, pair<Elem,int> y) { return x.second > y.second; }
};
它返回错误。我也尝试过这个。仍然返回错误。
pair<template <class Elem>, int>
class pairpairCompare {
public:
static bool lt(pair<Elem,int> x, pair<Elem,int> y) { return x.second < y.second; }
static bool eq(pair<Elem,int> x, pair<Elem,int> y) { return x.second == y.second; }
static bool gt(pair<Elem,int> x, pair<Elem,int> y) { return x.second > y.second; }
};
我知道这是一个简单的问题。但是我来自c＃background并且在查找上述函数的正确语法时遇到问题，因此我可以在此调用该函数。
maxheap<pair<char, int>,pairpairCompare> PairTtest(pairArr,0,maxArrayRoom);
要么
maxheap<pair<string, int>,pairpairCompare> PairTtest(pairArr,0,maxArrayRoom);
heap.h
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
using namespace std;
// Max-heap class
template <class Elem, class Comp> class maxheap {
private:
Elem* Heap; // Pointer to the heap array
int size; // Maximum size of the heap
int n; // Number of elements now in the heap
void siftdown(int); // Put element in its correct place
public:
maxheap(Elem* h, int num, int max) // Constructor
{ Heap = h; n = num; size = max; buildHeap(); }
int heapsize() const // Return current heap size
{ return n; }
bool isLeaf(int pos) const // TRUE if pos is a leaf
{ return (pos >= n/2) && (pos < n); }
int leftchild(int pos) const
{ return 2*pos + 1; } // Return leftchild position
int rightchild(int pos) const
{ return 2*pos + 2; } // Return rightchild position
int parent(int pos) const // Return parent position
{ return (pos-1)/2; }
bool insert(const Elem&); // Insert value into heap
bool removemax(Elem&); // Remove maximum value
bool remove(int, Elem&); // Remove from given position
void buildHeap() // Heapify contents of Heap
{ for (int i=n/2-1; i>=0; i--) siftdown(i); }
bool enqueue(int ObjID, int priority)
// inserting new element. Need the objid, priority, and reference to existing heap
{
pair<int,int> newPair=make_pair(ObjID,priority);//creating new pair
return insert(newPair);//calling maxheap->insert function. return success / failed.
}
bool dequeue()
//removing the highest priority. (priority)
{
pair<int,int> removedPair;//create pair to received removed value
if(removemax(removedPair))// call maxheap->remove max for removed pair
{
cout<<"Object ID of max priority: "<<removedPair.first<<endl;//show the removed object ID
return true;
}
else
{
cout<<"Nothing to remove"<<endl;
return false;
}
}
bool changeweight(int ObjID, int newPriority)
//changing the priority number of object ID
{
bool returnBool=false;//set return variable success or fail
for(int a=0;a<heapsize();a++)//sequential search to find object ID
{
if(pairArr[a].first==ObjID)//check whether object ID is the same
{
pairArr[a].second=newPriority;//update priority value
returnBool=true;//update return variable
break;//break array
}
}
if(returnBool)//if object ID is found
{
buildHeap();//need to rebuild the heap coz priority variable is changed.
}
return returnBool;//return success or fail
}
};
template <class Elem, class Comp> // Utility function
void maxheap<Elem, Comp>::siftdown(int pos) {
while (!isLeaf(pos)) { // Stop if pos is a leaf
int j = leftchild(pos); int rc = rightchild(pos);
if ((rc < n) && Comp::lt(Heap[j], Heap[rc]))
j = rc; // Set j to greater child's value
if (!Comp::lt(Heap[pos], Heap[j])) return; // Done
swap(Heap, pos, j);
pos = j; // Move down
}
}
template <class Elem, class Comp> // Insert element
bool maxheap<Elem, Comp>::insert(const Elem& val) {
if (n >= size) return false; // Heap is full
int curr = n++;
Heap[curr] = val; // Start at end of heap
// Now sift up until curr's parent > curr
while ((curr!=0) &&
(Comp::gt(Heap[curr], Heap[parent(curr)]))) {
swap(Heap, curr, parent(curr));
curr = parent(curr);
}
return true;
}
template <class Elem, class Comp> // Remove max value
bool maxheap<Elem, Comp>::removemax(Elem& it) {
if (n == 0) return false; // Heap is empty
swap(Heap, 0, --n); // Swap max with last value
if (n != 0) siftdown(0); // Siftdown new root val
it = Heap[n]; // Return deleted value
return true;
}
// Remove value at specified position
template <class Elem, class Comp>
bool maxheap<Elem, Comp>::remove(int pos, Elem& it) {
if ((pos < 0) || (pos >= n)) return false; // Bad pos
swap(Heap, pos, --n); // Swap with last value
while ((pos != 0) &&
(Comp::gt(Heap[pos], Heap[parent(pos)])))
swap(Heap, pos, parent(pos)); // Push up if large key
siftdown(pos); // Push down if small key
it = Heap[n];
return true;
}
/*
class pairpairCompare {
public:
static bool lt(pair<int,int> x, pair<int,int> y) { return x.second < y.second; }
static bool eq(pair<int,int> x, pair<int,int> y) { return x.second == y.second; }
static bool gt(pair<int,int> x, pair<int,int> y) { return x.second > y.second; }
};
*/
template<class Elem>
class pairpairCompare {
public:
static bool lt(pair<Elem,int> x, pair<Elem,int> y) { return x.second < y.second; }
static bool eq(pair<Elem,int> x, pair<Elem,int> y) { return x.second == y.second; }
static bool gt(pair<Elem,int> x, pair<Elem,int> y) { return x.second > y.second; }
};
template<class Elem>
inline void swap(Elem A[], int i, int j) {
Elem temp = A[i];
A[i] = A[j];
A[j] = temp;
}
Heap_Implement.cpp
#include "Heap.h"
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
using namespace std;
const int maxArrayRoom=20;// maximum array room. global variable.
pair<int, int>* pairArr=new pair<int, int>[maxArrayRoom];// creating a pair array with 2 integers
template <class Elem>
//choice 0 => negative values 1 => zero and negative values, 2 => same type is fine
void GetInputValue(Elem& elemInput,int choice)// checking input values for correct types and range
{
if(choice==0)//correct type and greater than 0 // use for integers
{
while (!(cin >> elemInput) || (elemInput<0) )
{
cin.clear(); //clear bad input flag
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); //discard input
cout << "Invalid input; please re-enter."<<endl;
}
}
if(choice==1)//correct type and greater than 1// use for integers
{
while (!(cin >> elemInput) || (elemInput<=0) )
{
cin.clear(); //clear bad input flag
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); //discard input
cout << "Invalid input; please re-enter."<<endl;
}
}
else if(choice==2)
{
while (!(cin >> elemInput))//correct type only. use for all types integers, double, char
{
cin.clear(); //clear bad input flag
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); //discard input
cout << "Invalid input; please re-enter."<<endl;
}
}
}
int main()
{
maxheap<pair<int, int>,pairpairCompare> PairTtest(pairArr,0,maxArrayRoom);//create heap with empty array
cout<<"Press=> 1 to add. 2 to remove. 3 to change. 4 to see all array. 0 to quit"<<endl;//menus
while(1)//infinite loop
{
int inputInt=-1;//create input variable
GetInputValue(inputInt,0);//get input
if(inputInt==1)//adding new priority
{
int ObjID, priority=-1;
cout<<"Key in Object ID"<<endl;//ask for object id
GetInputValue(ObjID,2);
cout<<"Key in priority"<<endl;//ask for priority id
GetInputValue(priority,2);
if(PairTtest.enqueue(ObjID,priority))//call enqueue to add. if succeeeded
{
cout<<"Succeeded"<<endl;
}
else//failed. may b array full / sth else
{
cout<<"Failed"<<endl;
}
}
else if(inputInt==2)//removing the max priority obj
{
PairTtest.dequeue();
}
else if(inputInt==3)//change the priority
{
int ObjID, priority=-1;
cout<<"Key in Object ID"<<endl;//ask for object id
GetInputValue(ObjID,2);
cout<<"Key in priority"<<endl;//ask for priority
GetInputValue(priority,2);
if(PairTtest.changeweight(ObjID,priority))//call changeweight
{
cout<<"Succeeded"<<endl;//success
}
else
{
cout<<"Failed"<<endl;//failure. may b object is not in array
}
}
else if(inputInt==4)//show heap array
{
cout<<"current size: "<<PairTtest.heapsize()<<endl;//show current size
cout<<"-> Object ID & Priority"<<endl;
for(int a=0;a<PairTtest.heapsize();a++)//loop to show all array
{
cout<<"-> "<< pairArr[a].first<< " & "<< pairArr[a].second<<endl;
}
cout<<"END of max heap"<<endl;
}
else if(inputInt==0)//quit
{
cout<<"BYE"<<endl;
break;//quit loop
}
else//invalid input
{
cout << "Invalid input; please re-enter."<<endl;
}
}
return 1;
}
答案 0 :(得分：0)
你发布的代码给我的错误是：
cannot convert 'std::pair<int, int>*' to 'std::pair<char, int>*'
你的第一个意图是好的，你需要改变的是：
pair<char, int>* pairArr=new pair<int, int>[maxArrayRoom];
pair<string, int>* pairArr=new pair<int, int>[maxArrayRoom];
通过
pair<char, int>* pairArr=new pair<char, int>[maxArrayRoom]; // note "new pair<char ...
pair<string, int>* pairArr=new pair<string, int>[maxArrayRoom]; // note "new pair<string ...
此外，您必须实例化pairpairCompare函数才能使用它，因为现在是一个模板：
maxheap<pair<char, int>, pairpairCompare<char, int> > PairTtest(pairArr,0,maxArrayRoom);
maxheap<pair<string, int>,pairpairCompare<string, int> > PairTtest(pairArr,0,maxArrayRoom);
当然，正如Jarod42所建议的那样，你可以使用矢量。
std::vector<std::pair<char, int> > pairArr(maxArrayRoom);
仍然需要向您提供代码的错误，这可能是此答案未涵盖的内容。我使用我们在您的问题中可以看到的信息来回答这个问题。