Calculate array sum by given array only, without passing it's length

Question

I need to calculate array sum, but attribute must be ONLY this particular array.

bool solution(int arr[]) {
    int counter = 0;
    int len = sizeof(arr) / sizeof(arr[0]);
    std::cout << len << std::endl;
    for (int i=0; i < len; i++){
        counter += arr[i];
    }
    if (counter == 21)
        return true;

    return false;
}

It won't work, I need to pass an array length from outside. how to reach this without passing array length as an attribute?

You can't. Arrays decay to pointers when passed into a function. — Christian Gibbons, Feb 19 '18 at 21:27
Why the restriction on not passing in the size? That's the preferred way to do it. — dbush, Feb 19 '18 at 21:28
In C++ one solution is to use a `std::vector`. It knows its own size. — Bo Persson, Feb 19 '18 at 21:30
How do you know how many numbers to sum without passing a length or quantity? Remember, I could have an array of 32 but only 10 slots are filled. — Thomas Matthews, Feb 19 '18 at 21:32
Pass the address of the array to `bool solution(int (*arr)[42]) {`. Of course, if the array count is not 42, then a compile time error. — chux - Reinstate Monica, Feb 19 '18 at 21:45

score 3 · Accepted Answer · answered Feb 19 '18 at 21:28

3

how to reach this without passing array length as an attribute?

You cannot unless your array holds a sentinel value that marks the end of valid numbers.

Use std::vector if you have the option to. Then, the size information comes along for the ride.

answered Feb 19 '18 at 21:28

R Sahu

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Calculate array sum by given array only, without passing it's length

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