How to print all values in a dynamically resizing struct? C++ - c++

I have a dynamically resizing struct[]. I ask the user for how many records he wants then make that many struct.Then I store the name and age info in the struct. The problem is when printing out that data i am only printing the last name and age the user input. I would like to print all the values.
struct Records
{
char name [32] ;
int age;
};
void program2()
{
Records rec;
int size;
cout << "How many record would you like?";
cin >> size;
cout << "\n" << size;
Records* a = new Records[size];
for (int i = 0; i < size; i++)
{
cout << "Whats the name for the Record: ";
cin >> rec.name;
cout << rec.name;
cout << "What is the age for this record: ";
cin >> rec.age;
}
for (int i = 0; i < size; i++)
{
cout << "\n" << rec.name << rec.age;
}
}

In your code, the variable rec has nothing to do with the array. To access the element at position i of your array, you'll need to use a[i].
For example:
cin >> a[i].name;
or
cout << "\n" << a[i].name << " " << a[i].age;

No surprise - you are actually printing repeatedly the last record that you created (rec). Your last loop is not actually traversing the array.
Also, the first loop only creates a struct, but does not actually add it to the array.
What you are trying to do is actually easier and cleaner if you use vectors instead of arrays, adding each record to the vector using push_back(). This is the closest thing to the "dynamically resized array" that you are referring to (such a thing does not actually exist in C++, that's what vectors are for, amongst other things).
Have a look into doing it this way, and if you get stuck feel free to ask again, happy to help.

Related

free or delete array of strcut c++

I made a simple array of struct I made a function to implement the array from users input
but I am struggling to find the right way to free or delete elements in the array ;
here is my code for a better understanding
#include <iostream>
using namespace std;
typedef struct InfStudent
{
int id;
int age;
int lvel;
}studentInfo;
void addElments(studentInfo *s)
{
int i=0;
for(i=0; i<2; i++) {
s[i].id = i;
s[i].age = i * i + 1;
s[i].lvel = i + i + 2;
}
}
int studCounter = 0 ;
void deltetElement(void *studentInfo1 ) {
for (int i = 0; i < 6; i++) {
cout << "empty " << endl;
free(studentInfo1);
}
}
int main()
{
int n;int i;
studentInfo st[2];
addElments(st);
for(i=0; i<2; i++) {
cout<<"enter the Id number of the student "<< endl;
cin >> st[i].id;
cout<<"enter the age of the student "<< endl;
cin >> st[i].age;
cout<<"enter the level of the student "<< endl;
cin >> st[i].lvel;
}
deltetElement(st);
for(i=0; i<2; i++) {
cout << "Id of the student " << i << "\t=" << st[i].id;
cout << "\t Age of the student " << i << "\t=" << st[i].age;
cout << "\tLevel of the student " << i << "\t=" << st[i].lvel;
cout<< endl;
}
return 0;
}
the output
enter the Id number of the student
1234
enter the age of the student
32
enter the level of the student
2
enter the Id number of the student
321
enter the age of the student
2
enter the level of the student
32
empty
it is printing empty, but the code still working like 3 second and then printing empty massage, but I did not understand it does delete or not, or there is a better way to do that;
Since you are using studentInfo st[2]; it's an array of VALUE types, meaning that studentInfo objects are not allocated in heap, and should not be deleted by free() or delete.
free or delete array of strcut c++
You create an array with automatic storage. Automatic objects are destroyed and their storage is released automatically when the variable goes out of scope. You cannot and you must not "free" them in any way other than by letting the execution proceed to the outside of the scope where the automatic object is defined.
Only thing that may be passed to free is a pointer that was returned by malloc (or certain other related C allocation functions) and hasn't previously been freed. Since that doesn't apply to what you pass to free, the behaviour of your program is undefined. That's bad. Don't do that.
P.S. Don't use malloc nor free in C++ if you can avoid it (and it can usually be avoided).
I am struggling to find the right way to free or delete elements in the array ;
The elements of an array are destroyed and their storage released when the array itself is destroyed and its memory is released. There is no way to separate those two.

How to write a code where user can give the elements of the array?

I wanted to write a code where user will give input the element of the array and then the elements will be print as an array. Here is my code but the code do not give the array as output.
#include<iostream>
using namespace std;
int main(){
int arr[100] , size , i , num ; //Here we are defining the maximum size of array is 100. So user can choose the size of array by him/her but cannot choose more than 100
cout << "Enter the size of array (Maximum array size you can take is 100) : ";
cin >> size;
if (size > 100)
{
cout << "You cannot take the size more than 100" << endl;
}else{
cout << "Inter the elements using space : ";
for (int i = 0; i < size; i++)
{
cin >> arr[i];
}
cout << "Enter data you want to insert : ";
cin >> num;
for (int i = size - 1 ; i >= 0 ; i--)
{
arr[i+1] = arr[i];
}
arr[0] = num;
size++;
}
cout << arr[i] << endl;
return 0;
}
Your question isn't entirely clear, but I see two basic problems.
First, you define variable i at the top of your code. That's fine, although there are arguments for variable names being longer than a single character. Think about searching for uses of that variable -- you're going to get it in all sorts of places that have nothing to do with the variable. while has an i. if has an i. Be that as it may.
But here's a real problem. You have some for loops like this:
for (int i = 0; ....)
There's nothing wrong with that, not exactly. It works. HOWEVER, it's considered bad form to reuse a variable inside an inner block that matches a variable from an outer block. It's legal, but it's a common source of bugs. I recommend you don't do it.
Then, at the bottom, you do this:
cout << arr[i] << endl;
At this point, we're back to the original variable i that you declare at the top. But you never actually initialize it, so it's some random value. And you're not doing any sort of loop.
I suspect if you wrap this inside another of your for-loops, you'd get the results you want.
And get rid of declaring i at the top.

My Vector is not printing despite print function [duplicate]

This question already has answers here:
How to pass objects to functions in C++?
(8 answers)
Closed 3 years ago.
I am working on a program that will establish a class of a Combo meal with specific parameters for the objects. I am storing these in a vector. The vector appears to be running appropriately but when I use the print function it is not printing anything. I need help getting the print function to operate appropriately.
I have tried using the .at() instead of getEntree() but still am not receiving any output. I have read several pieces on here about printing from a vector and still am unable to get any output from my program.
#include <iostream>
#include <string>
#include <vector>
#include "Combo.h"
void fillOrder(vector<Combo>);
void printOrder(vector<Combo>);
int main()
{
vector<Combo> myOrder;
fillOrder(myOrder);
printOrder(myOrder);
}
vector<Combo> newMyOrder;
void fillOrder(vector<Combo> newMyOrder) {
string entree;
string side;
string sideSize;
string drink;
string drinkSize;
cout << "How many meals would you like to order? ";
int orderSize;
cin >> orderSize;
for (int i=0; i < orderSize; i++) {
cout << "Would you like a Hamburger, Cheeseburger, or chicken?" << endl;
cin >> entree;
cout << "Would you like fries, tots, or a salad for your side?" << endl;
cin >> side;
cout << "What size would you like your side?" << endl;
cin >> sideSize;
cout << "What would you like to drink?" << endl;
cin >> drink;
cout << "What size drink would you like?" << endl;
cin >> drinkSize;
Combo newMeal(entree, side, sideSize, drink, drinkSize);
newMyOrder.push_back(newMeal);
}
}
void printOrder(vector<Combo>newMyCombo) {
unsigned int size = newMyCombo.size();
for (unsigned int i = 0; i < size; i++) {
cout << "Your Entree is : " << newMyCombo[i].getEntree()<<endl;
cout << "Your side is : " << newMyCombo[i].getSide()<<endl;
}
}
I am wanting this program to take the order then print a summary of the order, but I am getting no output at all.
Pass by reference
Try:
void fillOrder(vector<Combo>&);
void fillOrder(vector<Combo>& newMyOrder)
If you'd want the print function to not work on a copy (as it is just printing the orders) use void printOrder(const vector<Combo>&); instead. The const qualifier will give you a compile guarantee that a function that should not modify the container does not really do that. Passing this by reference to print will ensure that you don't waste time and space in copying the whole thing.

Transversing an Array of structs error in C++

Current code:
const int MAX_CODENAME = 25;
const int MAX_SPOTS = 5;
struct Team {
string TeamName[MAX_CODENAME];
short int totalLeagueGames;
short int leagueWins;
short int leagueLoses;
};
//GLOBAL VARIABLES:
Team league[MAX_SPOTS];
void addTeams(){
int i = 0; //first loop
int j; //second loop
while(i < MAX_SPOTS){
cout << "****** ADD TEAMS ******" << endl;
cout << "Enter the teams name " << endl;
scanf("%s", league[i].TeamName) ;
}
void searchTeam(){
string decider[MAX_CODENAME];
cout << "Please enter the team name you would like the program to retrieve: " << endl;
cin >> decider[MAX_CODENAME];
for(int i = 0; i < MAX_SPOTS; i++){
if(decider == league[i].TeamName){
cout << endl;
cout << league[i].TeamName << endl;
break;
}else{
cout << "Searching...." << endl;
}
}
}
I really dont know why its not working but I have included all the perquisite header files such as and but the program crashes when i enter the data and then attempt to search. I get the circle of death and then program not responding then says Process returned 255 (0xFF) . It does not even out put Searching.... the program practically gives up as soon as I enter that name.
Also if this can be optimized by the use of pointers that would be great.
tl;dr run-time error causing the search to fail as soon as i type in a name. And for the record I have checked to make sure the name I entered is valid.
scanf doesn't know about std::string. Use std::cin >> league[i].TeamName.
scanf("%s", league[i].TeamName) ;
This should be changed to
std::cin >> league[i].TeamName ;
A couple of other things here....
string decider[MAX_CODENAME];
cout << "Please enter the team name you would like the program to retrieve: " << endl;
cin >> decider[MAX_CODENAME];
Every time you input a value, you are telling the computer to hold the inputted value at decider[25] but the computer only reads indexes 0-24.
if(decider == league[i].TeamName){
Which array slot are you comparing the team name to? If its the 25th element than the statement should be
if(decider[24] == league[i].TeamName){
Pointers are better suited if the number of TeamNames are unknown. Based on the limited code presented, I highly recommend you stay within the realm of basic data types. For the purposes of troubleshooting, please post your full code in the future.
Your TeamName member variable:
string TeamName[MAX_CODENAME];
is an array of 25 strings, so in this line:
scanf("%s", league[i].TeamName) ;
you are courrupting the array. You don't really want an array anyways, so change the TeamName declaration to:
string TeamName;
and then when you read the name, you'll need to use iostreams which knows how to populate a string type (scanf only works with c char arrays):
std::cin >> league[i].TeamName

Bubble sorting in dynamic array of objects in C++

I have class City with following private data: name of city, width,length and height of the city. I have to make dynamic array, which is inserted by constructor by default- City(),when the programs starts.Then the program uses method output() and prints inserted array of cities.
I should use bubble sort to sort the cities by their length. And when this is done, the program should show the sorted cities in increasing lengths.
The problem is that my data are in private(in public everything works excellent but principle of capsulation is violated!) so I can't do bubble sort.
I tried to do another dynamic array of type double double Lengths[n], which content is lengths of first array. Then I do sorting, but program prints only sorted lengths and this is not my goal.
I should print the names of cities sorted by their lengths.
Code:
class City{
private: char *name;
double width;
double length;
double height;
public:void Output();
City();
~City();
double GetLength()
{
return length;
}
double GetWidth(){ return width; }
double GetHeight(){ return height; }
char GetName(){ return *name; }
};
City::City()
{
char ime[20];
cout << "Name= ";
cin >> ime;
name = new char[strlen(ime) + 1];
for (int i = 0; i <=strlen(ime); i++)
name[i] = ime[i];
cout << "Width= ";
cin >> width;
cout << "Length= ";
cin >> length;
cout << "Height= ";
cin >> height;
}
void City::Output()
{
cout << "Name is: " << name << endl;
cout << " Width is: " << width <<" deg"<< endl;;
cout << " Length is: " << length << " deg"<<endl;
cout << " Height is: " << height <<" m"<<endl;
return;
}
City::~City()
{
cout << " " << endl;
cout << "Destructor of City!" << endl;
delete[] name;
}
int main()
{
//City town;
//town.Input();
//town.Output();
int n;
City *mA;
cout << "Input number of cities: " << endl;
cin >> n;
mA = new City[n];
for (int j = 0; j < n; j++)
{
mA[j].Output();
}
cout << "Cities from west to east, sorted by their length" << endl;
double *Lengths = new double[n];
for (int j = 0; j < n; j++)
{
Lengths[j] = mA[j].GetLength();
}
int k = 0;//counter
double max = Lengths[0];
for (int j = 1; j < n; j++)
{
if (Lengths[j - 1] >Lengths[j])
{
max = Lengths[j - 1];
Lengths[j - 1] = Lengths[j];
Lengths[j] = max;
}
}
for (int j = 0; j < n; j++)//cycle for output
{
mA[j].Output();
}
delete[]mA;
return 0;
}
As I can't quite comment on your response, I will give you a few bits of advice. First in the line of:
Array[j]=mA[j].GetName() ;
You have a random space which may be a copy change and relatively minor but for reading purposes that is wrong.
Second your naming conventions are really something you should work on. I should be able to read a variable and understand what it means but instead I struggle to understand what a variable named mA means.
Third your else clause does nothing literally. Your not moving any parts of the array if that is your intention my saying this:
mA[j+1];
you are simply targeting the element in the array that is above the iteration. I see you stuck with your idea of making something similar to a parallel array for the bubble sort, and that is fine but you lack any action in the first loop.
This is not bubble sort what so ever as you are simply going through each iteration and checking if the element in Lengths is equal in length to the element in mA and then storing that element in array but your else statement does nothing.
Your loop should look similar to something like this but I'm gonna get rid of the character array and the extra array for some reason as it is unnecessary and lets say you start out with an array of your objects:
if(myObjects[i].GetLength() > myObjects[i+1].GetLength()) //Shortest to longest name or vice versa?
{
//Store myObject[i] in temp spot
//myObject[i] = myObject[i+1]
//myObject[i+1] = temp Storage
}
This will give you a bubble sort of the objects on the first round. Of course your going to have to find out how to iterate through the array in loop to verify all of the elements have been sorted correctly as this will of course take many iterations for bubble sort.
I don't see a direct question but I can assume majority of the question by your story. You have multiple options on how to solve this case. One of the simple ways to solve this is create a function within the object that allows you to get the length of a member of an object for example in your case it would be name of city.
Create a method inside the object that you can call to return a private method's length. Create a loop that calls this method and checks each element side by side until you can't refine it any longer. Is there a specific reason your using char instead of string for name?
I'm not entirely sure of what you're asking.
However, from what I can tell your main issue is that you can't sort because you're trying to compare two private variables from two objects.
If the objects are placed into an Array of type city, you can bubblesort by length however you would be required to use the getters in order to reference the variables that are private during sorting.
For example (not exact syntax)
if(cityArray[0].getLength() < cityArray[1].getLength())
{
//Do Something
}