typedef struct
{
int day;
int month;
int year;
} Date;
typedef struct
{
int a;
int s;
} MetaData;
struct A
{
char arrA[10];
char arrB[10];
Date date;
A(char * arrA, char *arrB, const Date& date)
{
strcpy(this->arrA, arrA);
strcpy(this->arrB, arrB);
this->date = date;
}
A(const A& a)
{
strcpy(this->arrA, a.arrA);
strcpy(this->arrB, a.arrB);
this->date = a.date;
}
};
bool operator < (const A & lhs, const A & rhs)
{
if(strcmp(lhs.arrA, rhs.arrA) == 0)
{
if(strcmp(lhs.arrB, lhs.arrB) == 0)
return false;
else return strcmp(lhs.arrB, lhs.arrB);
}
else
return strcmp(lhs.arrA, rhs.arrB);
}
typedef map<A, MetaData> TickerMap;
int main()
{
TickerMap tickerMap;
char x[10], y[10];
Date date;
A a(x, y, date);
MetaData m;
//tickerMap.insert(make_pair(a, m));
cout<<"The element is sucessfully inserted"<<endl;
return 0;
}
Whenever i create a struct with some constructors.It gives me run time error when i insert the object in the map. Can somebody please tell me the exact problem. It will be very helful. When I have normal structs ( C style) there is no problem during insertion.
Error :Run-Time Check Failure #2 - Stack around the variable 'date' was corrupted. (visual Studio)
x and y are uninitialized arrays, containing random garbage. In particular, they generally aren't NUL-terminated. When A's constructor strcpys from them, a buffer overrun occurs.
Your program exhibits undefined behavior. To the extent it appears to work with some compilers, it does so purely by accident.
Related
Below is a program that has class definitions for Item, Customer and Sales. The main simply creates object object of each class and test its member functions. Modify the main program such that it provides a menu driven interface where user can create objects of Item, Customer and a complete a sales transaction with the sales object.The program should also have an option for display the records of items,customers and sales.To make your program more useful,include file handling such that when objects are created for Items,Customers and Transaction,the user will be prompted to save the recordon the file or not.
here's the code it's not displaying anything pleasee help i'm running it by Dev c++
#include <conio.h>
#include <iostream>
#include <string.h>
using namespace std;
class Item {
int itemCode;
private:
double price;
double discount;
protected:
int qtyOnStock;
char *name;
public:
Item() {
itemCode = 0;
strcpy(name, "UNKNOWN");
price = 0;
discount = 0;
qtyOnStock = 100;
}
void setItemCode(int c) { itemCode = c; }
int getItemCode() { return itemCode; }
double getPrice() { return price; }
void setPrice(double p) { price = p; }
void setDiscount(double d) { discount = d; }
double getDiscount(double d) { return ((d < 20 ? d : 20) / 100 * price); }
void setName(char *n) { name = n; }
char *getName() { return name; }
void setQtyOnStock(int q) { qtyOnStock = q; }
int getQtyOnStock() { return qtyOnStock; }
};
class Customer {
private:
int id;
char *name;
char *contactNo;
int type;
public:
Customer() {
id = 0;
strcpy(contactNo, "No Num");
strcpy(name, "No Name");
type = 0;
}
void setId(int newId) { id = newId; }
int getId() { return id; }
void setName(char *n) { strcpy(name, n); }
char *getName() { return name; }
void setContactNo(char *c) { strcpy(contactNo, c); }
char *getContactNo() { return name; }
};
class Sales {
private:
Item item;
Customer cust;
char *date;
int qtySold;
public:
Sales() { date = "mm-dd-yyyy"; }
void setItem(Item newItem) { item = newItem; }
Item getItem() { return item; }
void setCustomer(Customer newCust) { cust = newCust; }
Customer getCustomer() { return cust; }
void setDate(char *newDate) { strcpy(date, newDate); }
char *getDate() { return date; }
void setQtySold(int newQty) { qtySold = newQty; }
int getQtySold() { return qtySold; }
};
int main() {
Item item1;
Customer cust1;
Sales sales1;
item1.setItemCode(143);
item1.setName("Ballpen");
item1.setPrice(12.5);
item1.setQtyOnStock(250);
cust1.setId(123);
cust1.setName("Juan dela Cruz");
sales1.setItem(item1);
sales1.setCustomer(cust1);
sales1.setDate("10-27-2018");
sales1.setQtySold(98);
item1.setQtyOnStock(item1.getQtyOnStock() - sales1.getQtySold());
system("cls");
cout << sales1.getItem().getName() << endl << item1.getQtyOnStock();
getch();
return 0;
}
The main and biggest proble is that you do C-style string handling with char* and even that in a wrong way.
If you would enable all warning in your compiler, it would already tell you the problems. My VS2019 gives 15 errors, 1 warning and 7 messages, when I try to compile your code. Please see:
So, the main problem is that you are using char* that are not initialzed, meaning they point to somehwere, and that you do not allocate memory to store your strings.
So all your strcpy functions will fail and probably crash your system. Also the assignments to a char* will fail in most cases.
You will overwrite some random memory.
All this can be immediately fixed, without big problems, if you would use std::string instead of char*. Because char* are that error prone, C++ introduced the std::string, so, please use it.
Sometimes you have C++ teachers that want you to use char*. Those teachers should be fired. But if you really need to use char*. Then you must allocate memory, before coping data.
Let us assume that you have a string "myName" and you want to copy that.
char* name{};
name = new char[strlen(myName)+1]; // +1 for the trailing '\0'
strcpy(name, myName);
// ...
// ...
// Do stuff
// ...
// ...
delete [] name; // Release memory at the end
But as said. Simply use std::string
Your program as is, cannot work. You need a major refactoring.
In your Item class:
protected:
int qtyOnStock;
char *name;
public:
Item() {
itemCode = 0;
strcpy(name, "UNKNOWN");
price = 0;
discount = 0;
qtyOnStock = 100;
}
name is an unitialized char pointer so copying to it will result in UB.
change char* name to std::string name, replace strcpy(...) name = "UNKNOWN".
Normally though you initialize member variables like this:
Item()
: itemCode(0), itemCode(0), name("UNKNOWN"), price(0), discount(0), qtyOnStrock(100)
{}
a newer compiler lets you initialize in other ways like when declared e.g.:
protected:
int qtyOnStock{100};
std::string name{"UNKNOWN"};
...
Okay so am trying to make a data structure that maintains a heap of data in order to solve within the compile-time limit. https://open.kattis.com/problems/annoyedcoworkers
I might be in over my head since I just started coding in the last year or so and I just learned about sorting and vectors last week and heap data structures yesterday. But I am really interested in solving this problem.
Anyway here goes I first started to solve this problem with selection sort... needless to say it took way too long.
Then I started looking into making a heap data structure that yields values sorted order,
which brought me to priority_queue
After about 9 hours of trying different methods, this is the closest I've gotten to solving the problem.
does anyone have any suggestions as to why after 25/27 test cases my code returns a wrong answer?
Here is my code :
// C++ program to use priority_queue to implement Min Heap
// for user defined class
#include <algorithm>
#include <iostream>
#include <queue>
#include <vector>
using namespace std;
// User defined class, coworker
class CoworkerT
{
private:
int a;
int d;
public:
CoworkerT(int _a, int _d)
{
a = _a;
d = _d;
}
int SimAddAD() const
{
int aD;
aD = a + d;
return aD;
}
int AddAD()
{
a = a + d;
return a;
}
int getA() const {
return a;
}
int getD() const {
return d;
}
};
// To compare two coworkers possible a value
class Min
{
public:
int operator() (const CoworkerT& p1, const CoworkerT& p2)
{
return p1.SimAddAD() > p2.SimAddAD();
}
};
//compare two a values between coworkers
class Max
{
public:
int operator() (const CoworkerT& p1, const CoworkerT& p2)
{
return p1.getA() < p2.getA();
}
};
int AskForA() {
int a;
cin >> a;
return a;
}
int AskForD() {
int d;
cin >> d;
return d;
}
priority_queue <CoworkerT, vector<CoworkerT>, Max >
PopulateMax(priority_queue <CoworkerT, vector<CoworkerT>, Max > max,
priority_queue <CoworkerT, vector<CoworkerT>, Min > min) {
while (min.empty() == false)
{
CoworkerT e = min.top();
max.push(CoworkerT(e.getA(), e.getD()));
min.pop();
}
return max;
}
// Driver code
int main()
{
int h, c, i, a, d;
cin >> h >> c;
// Creates a Min heap of points (order by possible a +d combination )
priority_queue <CoworkerT, vector<CoworkerT>, Min > pq;
// Creates a Max heap of points (order by actual a value )
priority_queue <CoworkerT, vector<CoworkerT>, Max > max;
// Insert points into the min heap
for (int i = 0; i < c; i++) {
a = AskForA();
d = AskForD();
pq.push(CoworkerT(a, d));
}
i = 0;
while (i < h) {
CoworkerT e = pq.top();
a = e.AddAD();
d = e.getD();
pq.pop();
pq.push(CoworkerT(a, d));
i++;
}
max = PopulateMax(max, pq);
CoworkerT eMax = max.top();
cout << eMax.getA() << endl;
return 0;
}
I just want to say that I ended up using something similar to my original algorithm using the heap. The problem was my use of int I switched to an unsigned long long int ~(though that might have been overkill?) and it worked like a charm.
// C++ program to use priority_queue to implement Min Heap
// for user defined class
#include <algorithm>
#include <iostream>
#include <vector>
#include <cmath>
using namespace std;
// User defined class, coworker
class CoworkerT {
private:
unsigned long long int a;
unsigned long long int d;
public:
CoworkerT(unsigned long long int _a, unsigned long long int _d){
a = _a;
d = _d;
}
unsigned long long int SimAddAD() const{
return a + d;
}
unsigned long long int AddAD(){
return a + d;;
}
unsigned long long int getA() const {
return a;
}
unsigned long long int getD() const {
return d;
}
};
//compare two coworkers possible a + d values
struct MinSort {
bool operator()(const CoworkerT& p1, const CoworkerT& p2) const {
return p1.SimAddAD() < p2.SimAddAD();
}
};
//compare two coworkers possible a + d values ~for some reason heap lesser than or greater need to be reverse of operator for sort???
struct Min {
bool operator()(const CoworkerT& p1, const CoworkerT& p2) const {
return p1.SimAddAD() > p2.SimAddAD();
}
};
//compare two a values between coworkers
struct MaxSort {
bool operator()(const CoworkerT& p1, const CoworkerT& p2) const {
return p1.getA() > p2.getA();
}
};
void FindAndPrintMax(vector<CoworkerT>& max) {
sort(max.begin(), max.end(), MaxSort());
CoworkerT minMax = max.front();
cout << minMax.getA();
}
void InputCoworkersAD(vector<CoworkerT>& min, unsigned long long int& h, unsigned long long int& c) {
int a, d, i;
cin >> h >> c;
// Insert a and d into the vector
if (h <= 100000 && h >= 1 && c <= 100000 && c >= 1) {
for (i = 0; i < c; i++) {
cin >> a >> d;
min.push_back(CoworkerT(a, d));
}
}
make_heap(min.begin(), min.end(), Min());
}
void AskForHelp(vector<CoworkerT>& min, unsigned long long int h) {
int i = 0;
while (i < h) {
push_heap(min.begin(), min.end(), Min());
CoworkerT e = min.front();
pop_heap(min.begin(), min.end(), Min());
min.pop_back();
min.push_back(CoworkerT(e.AddAD(), e.getD()));
i++;
}
}
// Driver code
int main()
{
unsigned long long int h, c;
vector<CoworkerT> min;
InputCoworkersAD(min, h, c);
AskForHelp(min, h);
FindAndPrintMax(min);
return 0;
}
I'm using the following example from Stroustrup C++ 4th Ed. Page 218. My question is regarding the destructor.
Questions:
How does placement new(&s) string{ss} allocate room for the new string when it's my understanding that union size is fixed to the largest member? Is string s not a 0 element string? If so, how does the placement new create a larger string if there is not enough space in the union?
#include <iostream>
#include <string>
using namespace std;
class Entry2 { // two alternative representations represented as a union
private:
enum class Tag { number, text };
Tag type; // discriminant
union { // representation
int i;
string s; // string has default constructor, copy operations, and destructor
};
public:
struct Bad_entry { }; // used for exceptions
string name;
Entry2(int n) : type{Tag::number}, i{n} { };
Entry2(string ss) : type{Tag::number} { new(&s) string{ss}; };
~Entry2();
Entry2& operator=(const Entry2&); Entry2(const Entry2&);
// ...
int number() const; string text() const;
void set_number(int n);
void set_text(const string&); // ...
};
Entry2::~Entry2()
{
if (type==Tag::text)
s.~string();
}
int Entry2::number() const
{
if (type!=Tag::number) throw Bad_entry{};
return i;
}
string Entry2::text() const
{
if (type!=Tag::text) throw Bad_entry{};
return s;
}
void Entry2::set_number(int n)
{
if (type==Tag::text) {
s.~string();
type = Tag::number;
}
i = n;
}
void Entry2::set_text(const string& ss)
{
if (type==Tag::text)
s = ss;
else {
new(&s) string{ss};
type = Tag::text;
}
}
Entry2& Entry2::operator=(const Entry2& e)
{
if (type==Tag::text && e.type==Tag::text) {
s = e.s; // usual string assignment
return *this;
}
if (type==Tag::text)
s.~string(); // explicit destroy (ยง11.2.4)
switch (e.type) {
case Tag::number:
i = e.i;
break;
case Tag::text:
new(&s) string{e.s};
type = e.type;
}
return *this;
}
int main(int argc, char *argv[])
{
Entry2 e0(0);
cout << e0.number() << endl;
try {
e0.text();
} catch (...) {
cout << "caught except" << endl;
}
e0.set_text("abcd");
cout << e0.text() << endl;
return 0;
}
No, the destructor should not always do this. Remember that in a union, only one of the fields is actually active at any one time. If the std::string member of the union isn't active, then calling its destructor would be a Bad Thing (cause undefined behavior) because there wasn't a string there to destroy. Instead, we instead only call the destructor on that std::string member if at some previous point in time we activated the std::string there.
Hope this helps!
I'm trying to compare two variables and the type of these variables are "Time". I can't seem to use the == / != function for these.
#include<iostream>
#include "Stock.h"
using namespace std;
void Stock::setShares(int d, int m, int y, int h, int mts, double p, int vol, double val)
{
date.setDate(d, m, y);
time.setTime(h, mts);
price = p;
value = val;
volume = vol;
}
Date Stock::getDate() const
{
return date;
}
Time Stock::getTime() const
{
return time;
}
This is in my main program:
Time t1, t2;
for (int i = 1; i < counter; ++i)
{
if (V1.at(i).getPrice() == highestPrice)
{
time2 = V1.at(i).getTime;
if (time2 != time1)
{
cout << time2;
}
}
}
How can I compare time1 & time2? I'm trying to avoid printing duplicate values of time in my program. V1 is a vector loaded with data from Stock object.
Check first whether == or != operator is overloaded for type Time. You must provide your own meaning to operators which you are gonna to use in your code for user-defined types else you will get compiler errors.
something like below,
class Time
{
public:
bool operator==(Time const & t1) const
{
return this.hour == t1.hour && this.min==t1.min;
}
private:
int min;
int hour;
};
In order to be able to answer your question completely, it would be necessary to know the details of the type "Time". Since you talk about comparing two objects, let's assume it is class.
If it was simple class like this:
class Time {
public:
int getValue();
void setValue(int value);
private:
int value;
}
You would need to use getValue method:
if( t1.getValue() == t2.getValue())
If you want to compare the objects directly, you need to overload the necessary operators:
bool operator==(const Time& anotherTime) const {
return (anotherTime.getValue()==this->getValue());
}
i am dealing with large dataset. May i ask you how it is possible to store strings in the classes i want to use with stxxl? I have read several discussions and everywhere was said that string is not POD type therefore it cannot be stored in the stxxl::vector, but i am not sure,because i tried it and i checked the data and everything seems to be fine. i have also saw an approach here https://github.com/Project-OSRM/osrm-backend/blob/725b93a961625a7b04d54806d7e0f80252a6bcd0/extractor/extraction_containers.hpp and they use stxxl::vector, so maybe the library got updated to support std::string?
class HighWay
{
private:
uint64_t id;
string name;
int speed;
string attributes; //additional attributes of way
string edges; //written uint64_t from,uint64_t to, int distance written as string
string nodes; //vector<uint64_t> written as string
public:
HighWay() = default;
void setId(uint64_t _id) {
id = boost::lexical_cast<string>(_id);
}
void setName(string _name) {
name = _name;
}
void setSpeed(int _speed) {
speed = _speed;
}
void setAttributes(string _attributes) {
attributes = _attributes;
}
void setEdges(string _edges) {
edges = _edges;
}
void setNodes(vector<uint64_t>refs) {
stringstream s;
uint64_t i = 0;
for (; i < refs.size()-1;i++) {
s << boost::lexical_cast<uint64_t>(refs[i]) << " ";
}
s << boost::lexical_cast<uint64_t>(refs[i]);
nodes = s.str();
}
uint64_t getId() {
return id;
}
string getName() {
return name;
}
int getSpeed() {
return speed;
}
string getAttributes() {
return attributes;
}
string getEdges() {
return edges;
}
std::vector<int64_t> getNodes() {
stringstream s(nodes);
uint64_t node;
std::vector<int64_t> result;
while (s >> node) {
result.push_back(static_cast<int64_t>(node));
}
return result;
}
};
I have also created code which stores the strings as POD,storing the string in vector of char and in map remembering lower and upper bound index in the array. But this approach leads to many std::maps used in the application.
//class to store in map
struct TypeName{
uint64_t start;
uint64_t end;
};
std::istream& operator >> (std::istream& i, TypeName& entry)
{
i >> entry.start;
i >> entry.end;
return i;
}
std::ostream& operator << (std::ostream& i, const TypeName& entry)
{
i << entry.start << " ";
i << entry.end;
return i;
}
struct PoiCategories{
uint64_t start;
uint64_t end;
};
std::istream& operator >> (std::istream& i,PoiCategories& entry)
{
i >> entry.start;
i >> entry.end;
return i;
}
std::ostream& operator << (std::ostream& i, const PoiCategories& entry)
{
i << entry.start << " ";
i << entry.end;
return i;
}
//object i want to store
struct Poi {
Poi() = default;
uint64_t id;
char type;
uint64_t id_in_pois; //id in vector pois
void addCategories(
vector<int> &kats, //categories to insert
stxxl::vector<uint64_t> &categories, //vector to store category
std::unordered_map <uint64_t, PoiCategories> &idPoi_categories //index to vector categories to retrieve all categories for Poi
)
{
size_t start = categories.size();
for (auto & kat : kats) {
categories.push_back(kat);
}
size_t end = categories.size() - 1;
idPoi_categories.insert(make_pair(id, PoiCategories{start, end }));
}
vector<int> getCategories(
stxxl::vector<uint64_t> &categories,
std::unordered_map <uint64_t, PoiKategorie> &idPoi_categories
)
{
std::vector<int> result;
PoiCategories bounds = idPoi_categories.find(id)->second;
for (size_t i = bounds.start; i <= bounds.end; i++) {
result.push_back(categories[i]);
}
return result;
}
};
Problem in my application is that i am storing a few string data, which are mainly names of streets and POIs. Maybe i am using wrong library. If so,can you recommend me a better approach to store data while preprocessing?
It's indeed banned, but the symptoms of violating the no-POD rule are generally unpredictable. It may very well appear to work as long as the strings all fit in memory, but in that case you didn't need the STXXL anyway.