# Array sum in C++ STL

In C++, we can quickly find array sum using accumulate()

`// C++ program to demonstrate working of accumulate()`
`#include <iostream> `
`#include <numeric>     `
`using` `namespace` `std;`
` `
`// User defined function that returns sum of`
`// arr[] using accumulate() library function.`
`int` `arraySum(``int` `a[], ``int` `n) `
`{`
`    ``int` `initial_sum  = 0; `
`    ``return` `accumulate(a, a+n, initial_sum);`
`}`
` `
`int` `main() `
`{`
`    ``int` `a[] = {5 , 10 , 15} ;`
`    ``int` `n = ``sizeof``(a)/``sizeof``(a[0]);`
`    ``cout << arraySum(a, n);`
`    ``return` `0;`
`}`

Output:

```30
```

Sum of vector

`// C++ program to demonstrate working of accumulate()`
`#include <iostream> `
`#include <vector> `
`#include <numeric>     `
`using` `namespace` `std;`
` `
`// User defined function that returns sum of`
`// arr[] using accumulate() library function.`
`int` `arraySum(vector<``int``> &v) `
`{`
`    ``int` `initial_sum  = 0; `
`    ``return` `accumulate(v.begin(), v.end(), initial_sum);`
`}`
` `
`int` `main() `
`{`
`    ``vector<``int``> v{5 , 10 , 15} ;`
`    ``cout << arraySum(v);`
`    ``return` `0;`
`}`

Output:

```30
```

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source and credits.
source and credits: http://www.geeksforgeeks.org
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