I am trying to work with dynamic arrays and somewhere in my code I have a segmentation fault that I cannot seem to find. I am not great at c++ classes yet. I have stared at this for hours and would appreciate any help that I can get. Thank you.
#include <iostream>
#include <stdlib.h>
#include <unistd.h>
usingnamespace std;
class Doubling {
private: //private variables
int *arr;
int size;
int used;
public:
Doubling() { //initializer
size = 2;
used = 0;
arr = newint[size]; //creating array, fill with zeros
for (int i = 0; i < size; i++) {
arr[i] = 0;
}
}
Doubling(int init[], int size) {
int *newer; //constructor
int i, j;
size = 2;
used = 0;
while (used >= size) { //if used is equal to size
newer = newint[size * 2]; //make a double sized array
for (i = 0; i < used; i++) {
newer[i] = arr[i]; //swap elements over to new array
}
for (j = used; j < size; j++) { //fill the rest with zeros
newer[j] = 0;
}
size = size * 2; //reset size
delete arr; //delete old array
arr = newer; // new array is now the array
}
}
void add(int toAdd) {
int *newer;
int m, n, y; //variables for add function
newer = newint[size * 2]{0}; //double size array
if ((used + toAdd) >= size) { // if used and to add is greater than size
for (m = 0; m < used; m++) {
newer[m] = arr[m]; //swap over elements
}
for (y=used; y < toAdd; y++) { //add whatever amount of random numbers
arr[y] = rand() % 10;
used++; //and increase used
toAdd--; //subtract toAdd
}
for (n = used; n < size; n++) { //fill the rest with zeros
newer[n] = 0;
}
}
size = size * 2; // the new size is now the size
// delete arr; //delete old array
arr = newer; //new array is now the array
}
void print() {
int k, l=0;
for (k=0, k < used; k++;) { //for all used elements
cout << "The array is " << getSize() << " elements long and contains the following numbers:" << endl;
if (l == 10){ //and a new line every ten elements
cout << endl;
l = 0;
}
else {
cout << arr[k] << ' '; //spit out used elements
l++;
}
}
}
int getSize() { //a size-getter
return size;
}
};
int main() {
Doubling d;
int var = 0;
cout << "please enter the number of elements to add: ";
cin >> var;
d.add(var);
cout << "after add" << endl;
d.print();
cout << "after print";
sleep(10);
return 0;
}
#include <iostream>
#include <stdlib.h> // remove this
#include <unistd.h> // remove this
usingnamespace std; // <-- remove this: it's for experts only.
class Doubling {
private: //private variables <-- remove all pointless comments like this
int *arr;
int size;
int used;
public:
Doubling() { //initializer <-- it's called constructor. Just remove this comment.
size = 2;
used = 0;
arr = newint[size]; //creating array, fill with zeros
for (int i = 0; i < size; i++) {
arr[i] = 0;
}
}
// Describe this overloaded constructor. What is it supposed to do?
// You neglect "init[]".
Doubling(int init[], int size) {
int *newer; //constructor <-- ???
int i, j;
size = 2;
used = 0;
while (used >= size) { //if used is equal to size
newer = newint[size * 2]; //make a double sized array
for (i = 0; i < used; i++) {
newer[i] = arr[i]; //swap elements over to new array
}
for (j = used; j < size; j++) { //fill the rest with zeros
newer[j] = 0;
}
size = size * 2; //reset size
delete arr; //delete old array
arr = newer; // new array is now the array
}
}
void add(int toAdd) {
int *newer;
int m, n, y; //variables for add function
newer = newint[size * 2]{0}; //double size array
if ((used + toAdd) >= size) { // if used and to add is greater than size
// ----------------------------------------------------------------------------
// --------> Here you copy everything into arr...
// ----------------------------------------------------------------------------
for (m = 0; m < used; m++) {
newer[m] = arr[m]; //swap over elements
}
for (y=used; y < toAdd; y++) { //add whatever amount of random numbers
arr[y] = rand() % 10;
used++; //and increase used
toAdd--; //subtract toAdd <-- Why?
}
for (n = used; n < size; n++) { //fill the rest with zeros
newer[n] = 0;
}
}
size = size * 2; // the new size is now the size
// delete arr; //delete old array
// ----------------------------------------------------------------------------
// ---> ...and here you tell arr to point to a new memory area.
// ----------------------------------------------------------------------------
arr = newer; //new array is now the array
}
void print() {
int k, l=0;
// Read compiler warnings:
// a) there's a comme instead of a semicolon
// b) there's an extra semicolon
for (k=0, k < used; k++;) { //for all used elements
// Move the following 'cout' outside the loop.
cout << "The array is " << getSize() << " elements long and contains the following numbers:" << endl;
if (l == 10){ //and a new line every ten elements
cout << endl;
l = 0;
}
else {
cout << arr[k] << ' '; //spit out used elements
l++;
}
}
}
int getSize() { //a size-getter
return size;
}
};
int main() {
Doubling d;
int var = 0;
cout << "please enter the number of elements to add: ";
cin >> var;
d.add(var);
cout << "after add" << endl;
d.print();
cout << "after print";
sleep(10);
return 0;
}
Anyway:
Bjarne Stroustrup, The C++ Programming Language - Fourth Edition, Chapter 4.6 Advice
Don’t reinvent the wheel; use libraries;
A different basic example of ‘dynamic array’ based on your code could be:
#include <iostream>
#include <limits>
class Doubling {
private:
int size; // max capacity before doubling
int used; // elements stored so far
int* arr;
public:
Doubling() : size { 2 }, used { 0 }, arr { newint[size]{} } {}
Doubling(int size_arg)
: size { size_arg }, used { 0 }, arr { newint[size]{} }
{}
void add(int to_be_added)
{
if(used < size) {
arr[used++] = to_be_added;
return;
}
int newsize = size * 2;
int* new_arr = newint[newsize] {};
for(int i{}; i<size; ++i) { new_arr[i] = arr[i]; }
new_arr[used++] = to_be_added;
delete[] arr;
arr = new_arr;
size = newsize;
}
void print() const
{
std::cout << "The array is " << used << " elements long and contains ""the following numbers:\n";
for (int k=0, l=0; k < used; k++) {
//and a new line every ten elements
if (l == 10) { std::cout << '\n'; l = 0; }
else { std::cout << arr[k] << ' '; l++; }
}
}
int getSize() const { return size; }
};
void waitForEnter();
int main() {
Doubling d;
std::cout << "please enter the number of elements to add: ";
int var = 0;
std::cin >> var;
for(int i{}; i<var; ++i) {
std::cout << "Next number to insert? ";
int num;
std::cin >> num;
d.add(num);
}
std::cout << '\n';
d.print();
waitForEnter();
return 0;
}
void waitForEnter()
{
std::cin.ignore(1000, '\n');
std::cout << "\nPress ENTER to continue...\n";
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
}
Output:
please enter the number of elements to add: 5
Next number to insert? 6
Next number to insert? 7
Next number to insert? 8
Next number to insert? 9
Next number to insert? 10
The array is 5 elements long and contains the following numbers
6 7 8 9 10
Press ENTER to continue...
