The built-in **`partial_sum()` function** is defined in the `<numeric>` header. The function takes partial sums of elements in an array and stores them in another array.

The partial sums of the array above are:

- y0 = x0

- y1 = x0 + x1

- y2 = x0 + x1 + x2

- y3 = x0 + x1 + x2 + x3

- y4 = x0 + x1 + x2 + x3 + x4

The partial sums will then be stored in another array as shown below.


#   
## Syntax
```
partial_sum(first, last, arrayB);
```

#   
## Arguments
1. `first`: Pointer to the first element in partial sum range (e.g., x0).
2. `last`: Pointer to the last element in partial sum range (e.g., x4).
3. `arrayB`: Array in which the sums are stored.

#    
## Return value
The function returns an iterator that points to past the last element that was added to `arrayB`. 

#include <iostream>
#include <numeric>
using namespace std;

int main() {
  const int sizeA = 5;
  int arrA[] = {1, 2, 3, 4, 5};
  int arrB[sizeA];

  cout << "Array A: ";
  for(int i = 0; i < sizeA; i++)
  {
    cout << arrA[i] << " ";
  }
  cout << endl;

  partial_sum(arrA, (arrA + sizeA), arrB);

  cout << "Array B: ";
  for(int i = 0; i < sizeA; i++)
  {
    cout << arrB[i] << " ";
  }
  cout << endl;

  return 0;
}

What is std::partial_sum() in C++?

Computes partial sums of array, storing results in another array and returning iterator past the last sum.

What is std::partial_sum() in C++?

Syntax

Arguments

Return value

Code