#include <iostream>
using namespace std;
/*
Animal cheapest(string type, Animal a[], int size) that returns the
cheapest animal in a of type type (that is, the cheapest cat or dog).
Note: Assuming you’ve
filled in an array of Animals called shelter, calling cheapest from your
main function would
look like
Animal inexpensive = cheapest(“Dog”, shelter, 20);
*/
struct Animal{
string name = "";
string gender = "";
int age = 0;
int price = 0;
string catOrDog = "";
};
Animal cheapest(string type, Animal a[], int size){
int smallest = a[0].price;
int indexOfSmallest = 0;
for(int i = 0; i<size; i++){
if(a[i].price < smallest && a[i].catOrDog == type){
indexOfSmallest = i;
}
}
return a[indexOfSmallest];
}
void printAnimal(Animal name){
cout<< name.name <<endl;
}
int main(){
Animal arr[1];
Animal one;
one.name = "Chad";
one.gender = "Female";
one.age = 2;
one.price = 1500;
one.catOrDog = "Dog";
Animal two;
two.name = "Brian";
two.gender = "Female";
two.age = 2;
two.price = 1000;
two.catOrDog = "Dog";
arr[0] = one;
arr[1] = two;
Animal inexpensive = cheapest("Dog", arr, 2);
printAnimal(inexpensive);
return 0;
}
Segmentation Error when running code. From what I've googled, this usually happens when you are reading from a file but I am not reading from a file.
What is wrong with my code? This is the first time I've encountered a problem like this so I am completely blank
You declare an array with one element:
Animal arr[1];
Then you access it out of bounds by storing two elements into it:
arr[0] = one;
arr[1] = two;
Only the first index (0) is valid.
You should consider using a std::array or std::vector rather than a C-style array, so you don't have to pass its size separately.
Related
I am having trouble passing an array of object pointers from main() to a function from different class.
I created an array of object pointers listPin main() and I want to modify the array with a function editProduct in class Manager such as adding new or edit object.
Furthermore, I want to pass the whole listP array instead of listP[index]. How to achieve this or is there any better way? Sorry, I am very new to c++.
#include <iostream>
using namespace std;
class Product
{
protected:
string id, name;
float price;
public:
Product()
{
id = "";
name = "";
price = 0;
}
Product(string _id, string _name, float _price)
{
id = _id;
name = _name;
price = _price;
}
};
class Manager
{
protected:
string id, pass;
public:
Manager(string _id, string _pass)
{
id = _id;
pass = _pass;
}
string getId() const { return id; }
string getPass() const { return pass; }
void editProduct(/*array of listP*/ )
{
//i can edit array of listP here without copying
}
};
int main()
{
int numProduct = 5;
int numManager = 2;
Product* listP[numProduct];
Manager* listM[numManager] = { new Manager("1","alex"), new Manager("2", "Felix") };
bool exist = false;
int index = 0;
for (int i = 0; i < numProduct; i++) { //initialize to default value
listP[i] = new Product();
}
string ID, PASS;
cin >> ID;
cin >> PASS;
for (int i = 0; i < numManager; i++)
{
if (listM[i]->getId() == ID && listM[i]->getPass() == PASS) {
exist = true;
index = i;
}
}
if (exist == true)
listM[index]->editProduct(/*array of listP */);
return 0;
}
Since the listP is a pointer to an array of Product, you have the following two option to pass it to the function.
The editProduct can be changed to accept the pointer to an array of size N, where N is the size of the passed pointer to the array, which is known at compile time:
template<std::size_t N>
void editProduct(Product* (&listP)[N])
{
// Now the listP can be edited, here without copying
}
or it must accept a pointer to an object, so that it can refer the array
void editProduct(Product** listP)
{
// find the array size for iterating through the elements
}
In above both cases, you will call the function as
listM[index]->editProduct(listP);
That been said, your code has a few issues.
First, the array sizes numProduct and numManager must be compiled time constants, so that you don't end up creating a non-standard variable length array.
Memory leak at the end of main as you have not deleted what you have newed.
Also be aware Why is "using namespace std;" considered bad practice?
You could have simply used std::array, or std::vector depending on where the object should be allocated in memory. By which, you would have avoided all these issues of memory leak as well as pointer syntaxes.
For example, using std::vector, you could do simply
#include <vector>
// in Manager class
void editProduct(std::vector<Product>& listP)
{
// listP.size() for size of the array.
// pass by reference and edit the listP!
}
in main()
// 5 Product objects, and initialize to default value
std::vector<Product> listP(5);
std::vector<Manager> listM{ {"1","alex"}, {"2", "Felix"} };
// ... other codes
for (const Manager& mgr : listM)
{
if (mgr.getId() == ID && mgr.getPass() == PASS)
{
// ... code
}
}
if (exist == true) {
listM[index]->editProduct(listP);
}
You cannot have arrays as parameters in C++, you can only have pointers. Since your array is an array of pointers you can use a double pointer to access the array.
void editProduct(Product** listP){
and
listM[index]->editProduct(listP);
Of course none of these arrays of pointers are necessary. You could simplify your code a lot if you just used regular arrays.
Product listP[numProduct];
Manager listM[numManager] = { Manager("1","alex"), Manager("2", "Felix")};
...
for(int i = 0; i < numManager; i++ ){
if(listM[i].getId() == ID && listM[i].getPass() == PASS) {
exist = true;
index = i;
}
}
if(exist == true){
listM[index].editProduct(listP);
}
Trying to learn datastructures, I made this class for a stack. It works just fine with integers but it throws a mysterious error with strings.
The class List is the API for my stack. Its meant to resize automatically when it reaches the limit. The whole code is just for the sake of learning but the error I get doesn't make any sense and it happens somewhere in some assembly code.
#include <iostream>
#include<string>
using namespace std;
class List {
private:
int N = 0;
string* list = new string[1];
void resize(int sz) {
max = sz;
string* oldlist = list;
string* list = new string[max];
for (int i = 0; i < N; i++) {
list[i] = oldlist[i];
}
}
int max = 1;
public:
void push(string str) {
if (N == max) {
resize(2 * N);
}
cout << max << endl;
list[N] = str;
N++;
}
void pop() {
cout << list[--N] << endl;
}
};
int main()
{
string in;
List list;
while (true) {
cin >> in;
if (in == "-") {
list.pop();
}
else {
list.push(in);
}
}
}
string* list = new string[max]; in the resize method defines a new variable named list that "shadows", replaces, the member variable list. The member list goes unchanged and the local variable list goes out of scope at the end of the function, losing all of the work.
To fix: Change
string* list = new string[max];
to
list = new string[max];
so that the function will use the member variable.
Don't forget to delete[] oldlist; when you're done with it to free up the storage it points at.
I'm trying to write a function that takes an array of structs and will sort the elements of the array alphabetically by accessing the first data member. I'm struggling to get the code to distinguish between when I'm referring to a data member versus initializing the size of an array. For example, the following code
void selectionSort(struct A[], int size)
{
int mindex;
for (int ct1 = 0; ct1 < size - 1; ct1++)
{
mindex = ct1;
for (int ct2 = ct1 + 1; ct2 < size; ct2++)
if (A[ct2].state < A[mindex].state)
mindex = ct2;
swap(A[mindex], A[ct1]);
}
}
complains that ct2 is not constant, when I'm clearly using it as an index. How would I get this to run correctly? That is, how can I get it to compare data members in their respective indices rather than think I'm initializing the size of a struct variable?
Edit The error message I am receiving is expression must have a constant value for the variable ct2.
I think you might have a problem with how you're creating your function. Usually, when you declare an array of structs it looks like this.
struct Student {
int uid;
string name;
};
Student studentArry[3];
You would use 'Student' or the name of your struct to initialize your array. For example, int arr[10] is an integer array of size 10 while Student arr[10] is a student array of size 10.
One other side note, if you're trying to create a function that is passed a struct you have to initialize the struct before you define the function. This code will work because the struct was declared before the function was.
#include <iostream>
using namespace std;
struct Student {
int uid;
string name;
};
void print(Student array[], int size){
for(int i = 0; i < size; i++){
cout << array[i].uid << endl;
cout <<array[i].name<< endl;
}
};
int main(){
Student StudentRecords[2] = {
{19, "John Smith"},
{21, "Jim Pop"}
};
print(StudentRecords, 2);
return 0;
}
The code below will not because the print function doesn't know what type student is.
#include <iostream>
using namespace std;
void print(Student array[], int size){
for(int i = 0; i < size; i++){
cout << array[i].uid << endl;
cout <<array[i].name<< endl;
}
};
int main(){
struct Student {
int uid;
string name;
};
Student StudentRecords[2] = {
{19, "John Smith"},
{21, "Jim Pop"}
};
print(StudentRecords, 2);
return 0;
}
So, all in all, I think you need to change how you're creating the parameter for the function and possible where you're declaring your struct.
I have no idea where the segmentation error is coming from ... Any ideas?
I am working with structures for an assignment
TestResult testResultFactory(std::string name, double mark)
{
//creating an object of TestResult
TestResult car;
car.name = name;
car.mark = mark;
return car;
}
Student studentFactrory(std::string name)
{
//Creating an object of student
Student house;
house.name = name;
house.testResults = 0;
house.numTestResults = 0;
return house;
}
void addTestResult(Student * student, std::string testName, double testMark)
{
//First we need to create a new array
(student->numTestResults)+=1;
TestResult *newTestArray = new TestResult[(student->numTestResults)];
//Now we loop through the old array and add it to the new one
int index = (student->numTestResults);
for (size_t i = 0; i < (index-1); i++)
{
newTestArray[i] = testResultFactory((student->testResults[i].name),(student->testResults[i].mark));
}
//Now we need to add the new student to the end of the array
newTestArray[index] = testResultFactory(testName, testMark);
(student->testResults) = newTestArray;
}
string studentBest(Student const * student)
{
//create variables as temps
string highestName;
double highestMark;
int index = (student->numTestResults);
//Setting the two variables to the first value
highestName = (student->testResults[0].name);
highestMark = (student->testResults[0].mark);
//Using a while loop to compare and get the best
for (size_t i = 0; i < index; i++)
{
if((student->testResults[i].mark)> highestMark)
{
highestMark = (student->testResults[i].mark);
highestName = (student->testResults[i].name);
}
}
//returning the string they want
string send = (highestName)+ " "+ doubleToString(highestMark)+ "%";
return send;
}
double studentAverage(Student const * student)
{
//Variables used as temps
double average = 0;
double counter = 0.0;
double running = 0;
int index = (student->numTestResults);
//Now we need to loop through each one and add to running and counter
for (size_t i = 0; i < index; i++)
{
counter++;
running += (student->testResults[i].mark);
}
//calculating the average;
average = (running)/counter;
return average;
}
void destroyStudent(Student * student)
{
delete [] (student->testResults);
(student->testResults)=0;
}
Subject subjectFactory(std::string name)
{
//Creating an object to use in subject factory
Subject lamp;
lamp.name = name;
lamp.numStudents = 0;
lamp.studentsAllocated = 0;
lamp.students = 0;
return lamp;
}
MY guess is that the error occurs because of an out of bounds array or an pointer not worked with correctly .
int getStudentIndex(Subject const * subject, std::string studentName)
{
int index;
int count = (subject->numStudents);
//loop to find the names and set index
for (size_t i = 0; i < count; i++)
{
if(studentName == ((subject->students[i].name)))
{
index = i;
}
else index = -1;
}
return index;
}
void addStudent(Subject * subject, std::string studentName)
{
//Variables as temps
Student *pointer =0;
int index = getStudentIndex(subject,studentName);
if(index != -1)
{
//Now we need to see if they are large enough
if((subject->studentsAllocated)==0)
{
//Set the allocated to 2
(subject->studentsAllocated) = 2;
pointer = new Student[2];
//Figure this out later
pointer[1] = studentFactrory(studentName);
(subject->students) = pointer;
}
else
{
//increase SA with 1.5
(subject->studentsAllocated) = (subject->studentsAllocated) * 1.5;
pointer = new Student[(subject->studentsAllocated)+1];
int count = (subject->studentsAllocated);
//Now we need to put all the other students in
for (size_t i = 0; i < count-1; i++)
{
pointer[i] = (subject->students[i]);
}
pointer[(subject->studentsAllocated)+1] = studentFactrory(studentName);
(subject->studentsAllocated) += 1 ;
}
//Once done just seet one equal to
(subject->students) = pointer;
}
else return;
}
void removeStudent(Subject * subject, std::string studentName)
{
//First get temps
int index = getStudentIndex(subject ,studentName);
int number = (subject->studentsAllocated);
int i = index;
//delete student
if(index == -1) return;
destroyStudent(&(subject->students)[index]);
//loop to shift the things
while (i<(number -1))
{
(subject->students)[i] = (subject-> students[i+1]);
}
//Removing the last one
(subject->numStudents) -= 1;
}
bool addTestResult(Subject * subject, std::string studentName, std::string testName, double testMark)
{
int index = getStudentIndex(subject ,studentName);
if(index != -1)
{
addTestResult(&(subject->students [index]),testName,testMark);
return true;
}
else
return false;
}
void printSubjectSummary(Subject const * subject)
{
cout<<(subject->name)<< ": with "<<(subject->numStudents)<<" students"<<endl;
//Variables to use in the loop
size_t indexLoop = subject->numStudents;
int i=0;
while (i< indexLoop)
{
cout<<(subject->students[i].name)<<" Average: "<<studentAverage(&(subject->students[i]))<<", Best: "<<studentBest(&(subject->students[i]))<<endl;
}
}
void destroySubject(Subject * subject)
{
//Variables
size_t indexLoop = subject->numStudents;
for (size_t i = 0; i < indexLoop; i++)
{
destroyStudent(&(subject->students[i]));
}
delete [] subject->students;
subject->students =0;
}
I can not seem to find where the segmentation error is coming from. Even restarted the whole assignment from scratch and still seem to get errors.
Can someone please help or indicate where the fault could be coming from.
Over here we have the structs.h file that is included in my code above
#ifndef STRUCTS_H
#define STRUCTS_H
struct TestResult{
double mark;//the test mark as a percentage
std::string name;//the test name
};
struct Student{
std::string name;
TestResult * testResults;//an arry of TestResults
size_t numTestResults;//the number of results for this student (also the size of the array)
};
struct Subject{
std::string name;
Student * students;//an array of Students
size_t numStudents;//the number of students added to the subject
size_t studentsAllocated;//the size of the Student arry(must never be smaller that numStudents)
};
#endif
There are so many logical errors in there that the root cause (or causes; there are quite a few candidates) could be pretty much anywhere.
getStudentIndex returns -1 unless the student is the last one in the array, and an indeterminate value for the first one you add, so adding the first student to a subject is undefined.
addStudent only adds a student if they're already taking the subject.
It also (for some inexplicable reason) allocates an array of two Students, leaving the first element uninitialised.
Using this first element is, of course, undefined.
In the other branch, it first claims that the number of allocated students is * 1.5, but then only allocates + 1.
This will undoubtedly lead to problems.
There is a recursion in addTestResult that will never terminate.
There are most likely other problems as well – this was just a quick glance.
Start with fixing these.
And do learn about constructors and destructors so you can get rid of those "factory" and "destroy" functions.
I'm writing a program that print the full english name of the number inputted by the user. it's not a complete program but i keep getting an error:
First-chance exception at 0x00b02c76 in Programming Challenge 14.1.exe: 0xC0000005: Access violation reading location 0xcccccd80.
Unhandled exception at 0x00b02c76 in Programming Challenge 14.1.exe: 0xC0000005: Access violation reading location 0xcccccd80.
I've tried looking around and couldn't find anything of use to me. here this the program:
header file:
#ifndef NUMBERS_H
#define NUMBERS_H
#include <string>
using namespace std;
const int SIZE1 = 18;
const int SIZE2 = 8;
class Numbers
{
private:
int number;
string hundred;
string thousand;
string * one;
string * ten;
public:
Numbers(int num)
{
number = num;
hundred = "hundred";
thousand = "thousand";
string * one = new string[SIZE1];
string * ten = new string[SIZE2];
}
void initializeArray()
{
// Intialize array "one"
one[0] = "zero";
one[1] = "one";
one[2] = "two";
one[3] = "three";
one[4] = "four";
one[5] = "five";
one[6] = "six";
one[7] = "seven";
one[8] = "eight";
one[9] = "nine";
one[10] = "eleven";
one[11] = "twelve";
one[12] = "thirteen";
one[13] = "fourteen";
one[14] = "fifteen";
one[15] = "sixteen";
one[16] = "seventeen";
one[17] = "eighteen";
one[18] = "nineteen";
// Initialize the ten array
ten[0] = "ten";
ten[1] = "twenty";
ten[2] = "thirty";
ten[3] = "forty";
ten[4] = "fifty";
ten[5] = "sixty";
ten[6] = "seventy";
ten[7] = "eighty";
ten[8] = "ninety";
}
string determine()
{
string name = "";
for (int i = 0; i <= number; i++)
{
if (number == i)
{
name = one[i];
}
}
return name;
}
~Numbers()
{
delete [] one;
delete [] ten;
}
};
#endif
and this is the main program, im just using a constructor to assign a value to number to make debugging a little faster
#include <iostream>
#include "Numbers.h"
using namespace std;
int main()
{
Numbers n(5);
string name = n.determine();
cout << "The number is " << name << endl;
cin.ignore();
cin.get();
return 0;
}
by the way this is vc++ for the compiler
ill answer any questions as this isnt really too organized
const int SIZE1 = 18;
Valid array index for the array of SIZE1 are 0 to 17. In general, valid indexes for an array of size N are 0 to N-1.
I recommend using std::vector<std::string>.
one holds 18 elements, but you put 19 elements in there.
Two things here:
You are not calling "initializeArray()" at all. So when you are trying to access the array there is nothing there. I would recommend calling it in the constructor. Like this:
Numbers(int num)
{
number = num;
hundred = "hundred";
thousand = "thousand";
one = new string[SIZE1];
ten = new string[SIZE2];
initializeArray();
}
Second, is what the guys above said. You have an incorrect value for the size of your array since you are trying to assign 19 values to an array of size 18. Just to be really sure lets make the size bigger than we expect and you can adjust later:
const int SIZE1 = 20;
const int SIZE2 = 20;
Additionally, See your determine()? instead of using a for loop why don't you go:
string name = one[number];
EDIT: Wow there was another thing I missed...you have declared your array pointer variable twice and so it's actually going out of scope thinking you want to make some local versions. Look at my adjusted implementation of your constructor above again. See how I've removed the "String *" from before the variable names.
The variable "one" and "ten" have been changed from string pointers to vectors holding strings. Called the initializeArray within the constructor. Changed the way the name string was being assigned the new string. Here is the working code.
class Numbers
{
private:
int number;
string hundred;
string thousand;
vector<string> one;
vector<string> ten;
public:
Numbers(int num)
{
number = num;
hundred = "hundred";
thousand = "thousand";
initializeArray();
}
void initializeArray()
{
one.push_back("zero");
one.push_back("one");
one.push_back( "two");
one.push_back("three");
one.push_back("four");
one.push_back("five");
one.push_back("six");
one.push_back("seven");
one.push_back("eight");
one.push_back("nine");
one.push_back("eleven");
one.push_back("twelve");
one.push_back("thirteen");
one.push_back("fourteen");
one.push_back("fifteen");
one.push_back("sixteen");
one.push_back("seventeen");
one.push_back("eighteen");
one.push_back("nineteen");
// Initialize the ten array
ten.push_back("ten");
ten.push_back("twenty");
ten.push_back("thirty");
ten.push_back("forty");
ten.push_back("fifty");
ten.push_back("sixty");
ten.push_back("seventy");
ten.push_back("eighty");
ten.push_back("ninety");
}
string determine()
{
string name("");
for (int i = 0; i <= number; i++)
{
if (number == i)
{
auto iter = one.begin();
iter += i;
name.assign(*iter);
}
}
return name;
}
~Numbers()
{
}
};
int main()
{
Numbers n(5);
string name = n.determine();
cout << "The number is " << name << endl;
cin.ignore();
cin.get();
return 0;
}