函数，数组和动态数组

Question

I have done this so far, i donot know where my mistake is or where im going wrong, I have come up with this program 1st time. We have to ask from the user amount of elements in an array which i have done using dynamic array. Then we have to pass 2 arguments one is the size of an array and the other is array(float type).

The function should replace the contents of each cell with the sum of the contents of all the cells in the original array from the left end to the cell in question. for example if i have array {1,2,3,4,5} function should return {1,3,6,10,15}. This is my program below please tell me what changes I have to make in my existing code.

#include <iostream>
using namespace std;

float compute(int x, float arr[]){
    float sum=0;

    for(int i=0; i<x;i++){
        sum+=arr[i];
        arr[i]=sum;
    }
    return arr;
}

int main(){
    int x;
    cout<<"How many elements you want"<<endl;
    cin>>x;

    float *p=new float[x];

    for(int i=0; i<x; i++){
        cin>>p[i];
    }
    cout<<compute(x,p);
    return 0;
}

Answer 1

Simple fixes, if you can modify original array

void compute(int x, float arr[]) 
{ 
    float sum=0;

    for(int i=1; i<x ;i++)
        arr[i] = arr[i] + arr[i-1];

    // return arr; // Not required
}

And then, you can do following

compute(x,p);
for(int i= 0 ; i< x; ++i)
   std::cout<< p[i] << std::endl;

Also, make sure to release the allocated memory, after processing

delete [] p;

Answer 2

Fix

#include <iostream>
using namespace std;

void compute(int x, float arr[]){
    float sum=0;

    for(int i=0; i<x;i++){
        sum+=arr[i];
        arr[i]=sum;
    }
}

int main(){

    int x;
    cout<<"How many elements you want"<<endl;
    cin>>x;

    float *p=new float[x];

    for(int i=0; i<x; i++){
        cin>>p[i];
    }

    for(int i=0; i<x; i++)
    {
        cout << p[i] << endl;
    }

    compute(x,p);
    cout << "----"<< endl;
    for(int i=0; i<x; i++)
    {
        cout << p[i] << endl;
    }
    delete[] p;
    return 0;
}

Notes

float compute(int x, float arr[])
{
...
return arr;
}

You declare the return type of compute as a float and then return arr which has the type of float[] . These types are not compatible.

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You cannot expect cout to print an array.

 cout<<compute(x,p);

In C and C++ an array is actually passed by the memory address of its first element. There is no way for cout to know how to print an array.

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When you create an array using new , you will always have to use the delete[] operator to free the memory you previously allocated.