I need some help here please.
I just started learning C++ (coming from Python background).
I'm trying to familiarize myself with arrays and functions. Wrote a bunch of functions to do as stated, above each one.
However, the function which is supposed to sum elements in an array and return their sum, seem to be adding 10 to the result, no matter the argument supplied as input. What am I doing wrong please, as I can't seem to find this out. Any help on general layout of my code also would be appreciated.
// WORKING WITH ARRAYS AND FUNCTIONS
#include<iostream>
using namespace std;
// FUNCTION TO INSTANTIATE ARRAY INT OF LENGTH N.
int* array_creator(int n)
{
static int ary_of_ten[10]; //declare array
for (int i=0; i<n; i++) //use loop to fill it up
{
ary_of_ten[i] = i+1;
}
return ary_of_ten;
}
//FUNCTION TO PRINT ARRAY ELEMENTS
void* array_printer(int arr[], int array_lenght)
{
for (int i=0; i<array_lenght-1; i++)
{
cout << arr[i] << " ";
}
cout << arr[array_lenght-1] << endl;
}
//FUNCTION ACCEPTS INT ARRAYS AND RETURNS ARRAY OF SQUARE OF EACH ELEMENT
int* square_array(int *p, int array_length)
{
const int ary_sz(array_length);
static int sqd_values[10];
for (int i=0; i<ary_sz; i++)
{
*(sqd_values + i) = *(p+i) * *(p+i);
}
return sqd_values;
}
//FUNCTION ACCEPTS INT ARRAYS AND RETURNS SUM OF ITS ELEMENTS
int sum_array(int *arry, int array_length)
{
int summation;
for(int i=0; i<array_length; i++)
{
summation += *(arry + i);
}
return summation;
}
int main()
{
cout << sum_array(array_creator(10), 3) << endl;
array_printer(array_creator(10), 10); //print array of 1-10 elements
array_printer(square_array(array_creator(10), 10), 10); //prt arry of sqrd values
return 0;
}
summation shuld be initialized to 0.
int summation=0;
Related
I have passed an array of size 10 to a funtion to sort the array reversely, but it's going wrong after rightly sorting first five elements of the array.
I want to sort the array 'std' reversely here,
# include <iostream>
using namespace std;
int reverse(int a[]); //funtion prototype
int main()
{
int std[10] = {0,1,2,3,4,5,6,7,8,9};
reverse(std);
}
int reverse(int a[]) //funtion defination
{
int index = 0;
for (int i = 9; i >= 0; i--)
{
a[index] = a[i]; //swaping values of the array
cout << a[index] << " ";
index++;
}
}
There's basically three things wrong with your code.
You aren't swapping anything
You have to swap the first half of the array with the second half, not swap the whole array. If you do that then everything gets swapped twice, so that nothing changes
You should print the reversed array after you have finished the reverse, not while you are doing the reverse.
Here's some code that fixes all these problems
# include <iostream>
# include <utility>
void reverse(int a[]);
int main()
{
int std[10] = {0,1,2,3,4,5,6,7,8,9};
reverse(std);
// print the array after reversing it
for (int i = 0; i < 10; ++i)
std::cout << std[i] << ' ';
std::cout << '\n';
}
void reverse(int a[])
{
for (int i = 0; i < 5; ++i) // swap the first half of the array with the second half
{
std::swap(a[i], a[9 - i]); // real swap
}
}
Yes you can.
I usually don't use "C" style arrays anymore (they can still be useful, but the don't behave like objects). When passing "C" style arrays to functions you kind of always have to manuall pass the size of the array as well (or make assumptions). Those can lead to bugs. (not to mention pointer decay)
Here is an example :
#include <array>
#include <iostream>
// using namespace std; NO unlearn trhis
template<std::size_t N>
void reverse(std::array<int, N>& values)
{
int index = 0;
// you only should run until the middle of the array (size/2)
// or you start swapping back values.
for (int i = values.size() / 2; i >= 0; i--, index++)
{
// for swapping objects/values C++ has std::swap
// using functions like this shows WHAT you are doing by giving it a name
std::swap(values[index], values[i]);
}
}
int main()
{
std::array<int,10> values{ 0,1,2,3,4,5,6,7,8,9 };
reverse(values);
for (const int value : values)
{
std::cout << value << " ";
}
return 0;
}
I am trying to use pointers whenever possible in the following code and am having difficulty figuring out how, exactly, to institute the pointers and how to return a pointer value at the end of my first function. I have done some research on the subject but none of the methods I found have been helpful so far, so I was hoping you may have some specialized tips.
Note: I am a beginner.
#include <iostream>
using namespace std;
int mode(int *pies[], int size) {
int count = 1;
int max = 0;
int *mode=pies[0];
for (int i=0; i<size-1; i++)
{
if (pies[i] == pies[i+1])
{
count++;
if (count>max)
{
max = count;
mode = pies[i];
}
}
else
count = 1;
}
return *mode;
}
int main() {
int n;
cout<<"Input the number of people: "<<endl;
cin>>n;
int survey[n];
cout << "Enter the amount of pie eaten by each person:" << endl;
for(int i = 0; i < n; i++) {
cout <<"Person "<<(i + 1)<< ": "<<endl;
cin>>survey[i];
}
cout<<"Mode: "<<mode(survey, n)<< endl;
return 0;
}
Here is an attempt to answer.
In your main(), you call the mode() function with mode(survey, n) while int survey[n]; is an array of int, so you may use int mode(int *pies, int size) instead of int mode(int *pies[], int size) (as the array int survey[n] can be implicitly converted into pointer).
However, you need to modify two more things in your function:
int *mode=pies[0]; is wrong as pies[0] is the first element of an array of int, thus is an int, while int* mode is a pointer on an int which is incompatible. mode should be an int to receive pies[0]. The correct code is then int mode = pies[0].
Your function signature is int mode(int *pies, int size), thus, again, you should return an int. You should then just return mode;
These are only hints on how to make the code compile.
Your next step is to formalize what you would like it to do and then modify the code accordingly
NB: The correct practice is to think about what you would like to achieve first and then code afterwards (but let us say that this is for the sake of helping each other)
To get started using pointers, you may look at some simple tutorials at first:
http://www.cplusplus.com/doc/tutorial/arrays/
https://www.programiz.com/c-programming/c-pointers
https://www.programiz.com/c-programming/c-pointers-arrays
https://www.geeksforgeeks.org/pointer-array-array-pointer/
https://www.geeksforgeeks.org/how-to-return-a-pointer-from-a-function-in-c/
https://www.tutorialspoint.com/cprogramming/c_return_pointer_from_functions.htm
Here is the modified code with the stated modifications above (it compiles):
#include <iostream>
using namespace std;
int mode(int *pies, int size) {
int count = 1;
int max = 0;
int mode=pies[0];
for (int i=0; i<size-1; i++)
{
if (pies[i] == pies[i+1])
{
count++;
if (count>max)
{
max = count;
mode = pies[i];
}
}
else
count = 1;
}
return mode;
}
int main() {
int n;
cout<<"Input the number of people: "<<endl;
cin>>n;
int survey[n];
cout << "Enter the amount of pie eaten by each person:" << endl;
for(int i = 0; i < n; i++) {
cout <<"Person "<<(i + 1)<< ": "<<endl;
cin>>survey[i];
}
cout<<"Mode: "<<mode(survey, n)<< endl;
return 0;
}
I was trying to store numbers in an array. The first half of the array are numbers that are ascending 1,2,3,4,5 etc and the second half of the array are random numbers. When i run the program it produces the output I wanted but gives me the error please help
#include <iostream>
#include <cstdlib>
using namespace std;
class sorting {
private:
int size, elements;
int arr[NULL];
public:
void sort(){
cout << "Enter number of desired elements" << ">"; cin >> elements;
arr[elements];
half();
}
void half() {
for (int i = 0; i < elements/2; i++) {
arr[i] = i + 1;
}
for (int i = elements / 2; i < elements; i++) {
arr[i] = rand();
}
cout << "This is the elements of the array";
for (int i = 0; i < elements; i++) {
cout << arr[i] << " ";
}
}
};
int main()
{
sorting sortObject;
sortObject.sort();
return 0;
}
As i could see you want the array size to change during run time depending on the input, we need to dynamically allocate a array.so take a integer pointer as a field instead of static array.
then inside the sort function after reading the input, dynamically allocate the memory to pointer.(actually its better if we do it in a constructor).
int *arr;
arr=(int *)malloc(elements*sizeof(int));
I need help with this code.
What I want is to make a parametric constructor and initialise/set the value of array in it.
Question: Make a class with arrays of integers and initialise it in a constructor. Then find the smallest and largest numbers using functions.
But I am stuck at how to initialise the array in the constructor.
I want to take data input in both ways
(1) By user, using cin
(2) By giving my own values
class Numbers
{
int Arr[3];
public:
Numbers() //default constructor
{
for (int i=0 ; i<=2 ; i++)
{
Arr[i]=0;
}
}
Numbers(int arr[]) //parameteric constructor
{
for (int i=0;i<=2;i++)
{
Arr[i]=arr[i];
}
}
};
int main()
{
int aro[3] = {0,10,5};
Numbers obj (aro);
return ;
}
The solution is pretty simple. I've made a new program from start again (for sake of understanding). According to your requirement, you wants to get input of array elements from the user dynamically and assign them to a constructor and use a method to print the highest value.
Consider the following code:
#include <iostream>
using namespace std;
const int N = 100;
class Numbers
{
int largest = 0;
public:
Numbers(int, int[]);
void showHighest(void)
{
cout << largest << endl;
}
};
Numbers::Numbers(int size, int arr[])
{
for (int i = 0; i < size; i++)
{
if (arr[i] > largest)
{
largest = arr[i];
}
}
}
int main(void)
{
int arrays[N], total;
cout << "How many elements? (starts from zero) ";
cin >> total;
for (int i = 0; i < total; i++)
{
cout << "Element " << i << ": ";
cin >> arrays[i];
}
Numbers n(total, arrays);
n.showHighest();
return 0;
}
Output
How many elements? (starts from zero) 3
Element 0: 12
Element 1: 16
Element 2: 11
16
Note: I've initialized a constant number of maximum elements, you can modify it. No vectors, etc. required to achieve so. You can either use your own values by removing the total and its followed statements and use only int arrays[<num>] = {...} instead. You're done!
Enjoy coding!
I suggest to use std::vector<int> or std::array<int>.
If you want initialize with custom values you can do std::vector<int> m_vec {0, 1, 2};
Thank you so much for your help. I was basically confused about how to use arrays in a constructor and use setters/getters for arrays in a class. But you all helped a lot. Thanks again.
Numbers(int arr[])
{
for (int i=0;i<=9;i++)
{
Arr[i]=arr[i];
}
Largest=Arr[0];
Smallest=Arr[0];
}
void Largest_Number()
{
header_top("Largest Number");
Largest=Arr[0]; //Using this so we make largest value as index zero
for (int i=0 ; i<=9 ; i++)
{
if(Arr[i]>Largest)
{
setLargest( Arr[i] );
}
}
cout<<"Largest Number: "<<getLargest()<<endl;
}
my code is not working it is producing unexpected results.the code is about array rotation by using a temp array . function "rotate" rotates the array , while function printArray prints the array .in the main function both functions are called. then there is cout with "hello". the overall output if "ellolloloohello". why am i getting this output.thanks
#include<iostream>
using namespace std;
void rotate(int arr[],int d, int n){
int temp[d];
for(int i =0;i<d;i++){
temp[i]=arr[i];
}
for(int i = 0;i<n-d;i++){
arr[i] = arr[i+d];
}
for(int i =0 ;i < d;i++)
{
temp[i]= arr[n-d+i];
}
}
void printArray(int arr[],int size){
for(int i =0;i<size;i++)
{
cout<<arr[i]+" " ;
}
}
int main()
{
int arr[10] = {0,1,2,3,4,5,6,7,8,9};
rotate(arr,3,10);
printArray(arr,10);
cout <<"hello";
}
;
the output is "ellolloloohello" instead of "hello". whats happening here?????
For starters the variable length arrays
void rotate(int arr[],int d, int n){
int temp[d];
//...
is not a standard C++ feature. Either use an auxiliary standard container as for example std::vector or std::list or you should dynamically allocate an array.
In the last loop of the function
void rotate(int arr[],int d, int n){
int temp[d];
for(int i =0;i<d;i++){
temp[i]=arr[i];
}
for(int i = 0;i<n-d;i++){
arr[i] = arr[i+d];
}
for(int i =0 ;i < d;i++)
{
temp[i]= arr[n-d+i];
}
}
you are overwriting the array temp instead of the array arr.
And in the function printArray in this statement
cout<<arr[i]+" " ;
in the expression
arr[i]+" "
there is used the pointer arithmetic. That is the string literal " " is implicitly converted to pointer to its first element and the numeric value arr[i] is used as an offset for this pointer. Instead write
cout<<arr[i] << " " ;
Change cout<<arr[i]+" " ; to cout << arr[i] << ' ';
And please use std::vector. int arr[d] is no c++ :(