我一直收到“降雨最多= NULL”的错误。在尝试初始化时排队。无法将int转换为Rainfall。我无法弄清楚我做错了什么。总共有四个文件，我真的很感激任何帮助。
MAIN
// This program demonstrates the linked list template.
#include <iostream>
#include "RainfallList.h"
#include "Rainfall.h"
using namespace std;
int main()
{
// Define a LinkedList object.
RainfallList<Rainfall> list;
Rainfall most = NULL;
//Rainfall least = NULL;
int entries = 0;
bool marker = false;
int month = 0;
int year = 0;
double rainfall = 0.0;
double total = 0.0;
cout << "Enter the number of entries you would like: ";
cin >> entries;
//Create linked list of values
for(int i=1; i<=entries; i++){
marker=false;
while(marker==false){
cout << "Enter the month for entry " << i << " (1-12): ";
cin >> month;
cout << "Enter the year for entry " << i << " (2010-2013): ";
cin >> year;
cout << "Enter the rainfall for entry " << i << " (inches): ";
cin >> rainfall;
if(month>0 && month<13 && year>2009 && year<2014 && rainfall>=0){
marker=true;
}else{
cout << endl << endl << "**ERROR** Make sure the month is a value from 1-12, the year is 2010-2013, and rainfall is 0 or greater!" << endl << endl;
}
}
Rainfall value(year, month, rainfall);
list.appendNode(value);
}
list.displayList();
//find average rainfall
total = list.getAvg();
cout << "The total amount of rainfall is " << total << " inches." << endl;
cout << "The average rainfall is " << total/entries << " inches" << endl;
//find the month with the highest rainfall
most = list.getMost();
cout << "The most rainfall happened in " << most.getMonth() << " of " << most.getYear() << " where it rained " << most.getRainfall() << " inches." << endl;
//find the month with the lowest rainfall
most = list.getLeast();
cout << "The most rainfall happened in " << most.getMonth() << " of " << most.getYear() << " where it rained " << most.getRainfall() << " inches." << endl;
system("Pause");
return 0;
}
链表
// A class template for holding a linked list.
// The node type is also a class template.
#ifndef RainfallList_H
#define RainfallList_H
#include "Rainfall.h"
//*********************************************
// The ListNode class creates a type used to *
// store a node of the linked list. *
//*********************************************
template <class T>
class RainfallListNode
{
public:
T value; // Node value
RainfallListNode<T> *next; // Pointer to the next node
// Constructor
RainfallListNode(T nodeValue)
{
value = nodeValue;
next = NULL;
}
};
//*********************************************
// LinkedList class *
//*********************************************
template <class T>
class RainfallList:Rainfall
{
private:
RainfallListNode<T> *head; // List head pointer
public:
// Constructor
RainfallList()
{
head = NULL;
}
// Destructor
~RainfallList();
// Linked list operations
void appendNode(T);
void insertNode(T);
void deleteNode(T);
void displayList() const;
double getAvg();
Rainfall getMost();
Rainfall getLeast();
};
//**************************************************
// appendNode appends a node containing the value *
// pased into newValue, to the end of the list. *
//**************************************************
template <class T>
void RainfallList<T>::appendNode(T newValue)
{
RainfallListNode<T> *newNode; // To point to a new node
RainfallListNode<T> *nodePtr; // To move through the list
// Allocate a new node and store newValue there.
newNode = new RainfallListNode<T>(newValue);
// If there are no nodes in the list
// make newNode the first node.
if (!head)
head = newNode;
else // Otherwise, insert newNode at end.
{
// Initialize nodePtr to head of list.
nodePtr = head;
// Find the last node in the list.
while (nodePtr->next)
nodePtr = nodePtr->next;
// Insert newNode as the last node.
nodePtr->next = newNode;
}
}
//**************************************************
// displayList shows the value stored in each node *
// of the linked list pointed to by head. *
//**************************************************
template <class T>
void RainfallList<T>::displayList() const
{
RainfallListNode<T> *nodePtr; // To move through the list
// Position nodePtr at the head of the list.
nodePtr = head;
// While nodePtr points to a node, traverse
// the list.
while (nodePtr)
{
// Display the value in this node.
cout << nodePtr->value << endl;
// Move to the next node.
nodePtr = nodePtr->next;
}
}
//**************************************************
// The insertNode function inserts a node with *
// newValue copied to its value member. *
//**************************************************
template <class T>
void RainfallList<T>::insertNode(T newValue)
{
RainfallListNode<T> *newNode; // A new node
RainfallListNode<T> *nodePtr; // To traverse the list
RainfallListNode<T> *previousNode = NULL; // The previous node
// Allocate a new node and store newValue there.
newNode = new RainfallListNode<T>(newValue);
// If there are no nodes in the list
// make newNode the first node
if (!head)
{
head = newNode;
newNode->next = NULL;
}
else // Otherwise, insert newNode
{
// Position nodePtr at the head of list.
nodePtr = head;
// Initialize previousNode to NULL.
previousNode = NULL;
// Skip all nodes whose value is less than newValue.
while (nodePtr != NULL && nodePtr->value < newValue)
{
previousNode = nodePtr;
nodePtr = nodePtr->next;
}
// If the new node is to be the 1st in the list,
// insert it before all other nodes.
if (previousNode == NULL)
{
head = newNode;
newNode->next = nodePtr;
}
else // Otherwise insert after the previous node.
{
previousNode->next = newNode;
newNode->next = nodePtr;
}
}
}
//*****************************************************
// The deleteNode function searches for a node *
// with searchValue as its value. The node, if found, *
// is deleted from the list and from memory. *
//*****************************************************
template <class T>
void RainfallList<T>::deleteNode(T searchValue)
{
RainfallListNode<T> *nodePtr; // To traverse the list
RainfallListNode<T> *previousNode = nullptr; // To point to the previous node
// If the list is empty, do nothing.
if (!head)
return;
// Determine if the first node is the one.
if (head->value == searchValue)
{
nodePtr = head->next;
delete head;
head = nodePtr;
}
else
{
// Initialize nodePtr to head of list
nodePtr = head;
// Skip all nodes whose value member is
// not equal to num.
while (nodePtr != NULL && nodePtr->value != searchValue)
{
previousNode = nodePtr;
nodePtr = nodePtr->next;
}
// If nodePtr is not at the end of the list,
// link the previous node to the node after
// nodePtr, then delete nodePtr.
if (nodePtr)
{
previousNode->next = nodePtr->next;
delete nodePtr;
}
}
}
//**************************************************
// Destructor *
// This function deletes every node in the list. *
//**************************************************
template <class T>
RainfallList<T>::~RainfallList()
{
RainfallListNode<T> *nodePtr; // To traverse the list
RainfallListNode<T> *nextNode; // To point to the next node
// Position nodePtr at the head of the list.
nodePtr = head;
// While nodePtr is not at the end of the list...
while (nodePtr != NULL)
{
// Save a pointer to the next node.
nextNode = nodePtr->next;
// Delete the current node.
delete nodePtr;
// Position nodePtr at the next node.
nodePtr = nextNode;
}
}
template <class T>
double RainfallList<T>::getAvg()
{
double avg = 0.0;
Rainfall obj;
RainfallListNode<T> *nodePtr; // To move through the list
// Position nodePtr at the head of the list.
nodePtr = head;
// While nodePtr points to a node, traverse
// the list.
while (nodePtr)
{
// Display the value in this node.
//cout << nodePtr->value << endl;
obj = nodePtr->value;
avg += obj.getRainfall();
// Move to the next node.
nodePtr = nodePtr->next;
}
return avg;
}
template <class T>
Rainfall RainfallList<T>::getMost()
{
//double avg = 0.0;
Rainfall obj = NULL;
Rainfall obj2 = NULL;
RainfallListNode<T> *nodePtr; // To move through the list
// Position nodePtr at the head of the list.
nodePtr = head;
obj = nodePtr->value;
// While nodePtr points to a node, traverse
// the list.
while (nodePtr)
{
// Display the value in this node.
//cout << nodePtr->value << endl;
obj2 = nodePtr->value;
if (obj.getRainfall() < obj2.getRainfall()){
obj = nodePtr->value;
}
// Move to the next node.
nodePtr = nodePtr->next;
}
return obj;
}
template <class T>
Rainfall RainfallList<T>::getLeast()
{
//double avg = 0.0;
Rainfall obj = NULL;
Rainfall obj2 = NULL;
RainfallListNode<T> *nodePtr; // To move through the list
// Position nodePtr at the head of the list.
nodePtr = head;
obj = nodePtr->value;
// While nodePtr points to a node, traverse
// the list.
while (nodePtr)
{
// Display the value in this node.
//cout << nodePtr->value << endl;
obj2 = nodePtr->value;
if (obj.getRainfall() > obj2.getRainfall()){
obj = nodePtr->value;
}
// Move to the next node.
nodePtr = nodePtr->next;
}
return obj;
}
#endif
RAINFALL CLASS
#ifndef RAINFALL_H
#define RAINFALL_H
#include <iostream>
using namespace std;
//class rainclass;
//ostream &operator << (ostream & , const Rainfall & );
//istream &operator >> (istream & , Rainfall & );
class Rainfall
{
private:
int year;
int month;
double rainfall;
public:
Rainfall(void);
Rainfall(int year, int month, double rainfall);
void setRain(int year, int month, double rainfall);
int getYear();
int getMonth();
double getRainfall();
void print();
// Overloaded operator functions
Rainfall operator + (const Rainfall &); // Overloaded +
//Rainfall operator - (const Rainfall &); // Overloaded -
//Rainfall operator ++ (); // Prefix ++
//Rainfall operator ++ (int); // Postfix ++
bool operator > (const Rainfall &); // Overloaded >
bool operator < (const Rainfall &); // Overloaded <
//bool operator == (const Rainfall &); // Overloaded ==
//bool operator != (const Rainfall &); // Overloaded ==
// Conversion functions
//operator double();
//operator int();
// Friends
friend ostream &operator << (ostream &, const Rainfall &);
//friend istream &operator >> (istream &, Rainfall &);
};
#endif
降雨实施
#include "Rainfall.h"
#include <iostream>
using namespace std;
Rainfall::Rainfall(){
year = 0;
month = 0;
rainfall = 0.0;
}
Rainfall::Rainfall(int tempyear, int tempmonth, double temprainfall){
year = tempyear;
month = tempmonth;
rainfall = temprainfall;
}
void Rainfall::setRain(int tempyear, int tempmonth, double temprainfall){
year = tempyear;
month = tempmonth;
rainfall = temprainfall;
}
int Rainfall::getMonth() {
return month;
}
int Rainfall::getYear() {
return year;
}
double Rainfall::getRainfall() {
return rainfall;
}
void Rainfall::print() {
cout << "There was " << getRainfall() << " inches of rainfall in " << getMonth() << " of " << getYear() << endl;
}
//**********************************************
// Overloaded binary + operator. *
//**********************************************
Rainfall Rainfall::operator + (const Rainfall &right)
{
Rainfall temp;
//temp.year = year + right.year;
//temp.month = month + right.month;
temp.rainfall = rainfall + right.rainfall;
return temp;
}
//********************************************************
// Overloaded << operator. Gives cout the ability to *
// directly display FeetInches objects. *
//********************************************************
ostream &operator<<(ostream &strm, const Rainfall &obj)
{
strm << obj.month << " " << obj.year << " " << obj.rainfall << "inches" << endl;
return strm;
}
//************************************************************
// Overloaded > operator. Returns true if the current object *
// is set to a value greater than that of right. *
//************************************************************
bool Rainfall::operator > (const Rainfall &right)
{
bool status;
if (rainfall > right.rainfall)
status = true;
//else if (feet == right.feet && inches > right.inches)
//status = true;
else
status = false;
return status;
}
//************************************************************
// Overloaded < operator. Returns true if the current object *
// is set to a value less than that of right. *
//************************************************************
bool Rainfall::operator < (const Rainfall &right)
{
bool status;
if (rainfall < right.rainfall)
status = true;
//else if (feet == right.feet && inches < right.inches)
//status = true;
else
status = false;
return status;
}
答案 0 :(得分：0)
你可以用NULL初始化一个指针，但是在一个对象（在你的情况下为Rainfall）中指定NULL（在幕后是一个int）是没有意义的。
Rainfall most;
就足够了，因为你的Rainfall构造函数已经默认使用零初始化新对象。