Why is my program saying that 5 * 5 is equal to 104126025?

Question

I created a function to return the result of all the odd numbers in a vector.

    int oddProduct(std::vector<int> arr) {
    int sum = 1;

    for (int i = 0; i <= arr.size(); i++) {
        if (arr[i] % 2 != 0){
            sum *= arr[i];
            std::cout << " " << arr[i];
            }
         }
    return sum;
    }

The function worked with every other vector I inputted and the print statements even show that the elements of the vector I multiply are both equal to 5. (btw I was using repl.it)

please post a [mcve]. include input,output and expected output in the question — 463035818_is_not_an_ai, Oct 16 '20 at 14:25
btw "the result of all odd numbers" ... result of what? Are you confusing `+` and `*` ? At least `sum` is not a sum — 463035818_is_not_an_ai, Oct 16 '20 at 14:27
You would have cleaner code and avoid the bug if you used an iterator instead of an integer index variable. — Nate Eldredge, Oct 16 '20 at 14:29
@MikeCAT I was just about to suggest that. It's the best gift to loops ever. :-) — Ted Lyngmo, Oct 16 '20 at 14:31
@MikeCAT I think that using `std::accumulate` with lambda will also be nice. :) `return std::accumulate(arr.begin(), arr.end(), 1, [](auto a, auto b) { return a * (b % 2 ? b : 1); });` — brc-dd, Oct 16 '20 at 14:32
If you look more closely at examples, you will notice that they say `<`, not `<=`. — molbdnilo, Oct 16 '20 at 14:32

JDługosz · Answer 1 · 2020-10-16T14:32:30.313

3

i <= arr.size()
The legal values of the subscript are 0 through size-1 inclusive.

Use a range-based for statement to avoid the mistake (and the repeated dereferences)

edited Oct 16 '20 at 14:32

answered Oct 16 '20 at 14:31

JDługosz

5,592
3
24
45

1

a range based for loop does not avoid repeated dereferencing, its just hidden, maybe thats what you mean – 463035818_is_not_an_ai Oct 16 '20 at 14:33
2

btw if thats the whole answer I'd rather look for a duplicate or (what i did) vote to close as typo, just saying – 463035818_is_not_an_ai Oct 16 '20 at 14:35
a range-based for loop will dereference the iterator once and give you a name for that value. – JDługosz Oct 16 '20 at 19:03
ok now I understand, but still you can do the same in a non-range based loop, number of dereferences is the same just hidden from the user. Nevermind, just wasnt sure what you mean – 463035818_is_not_an_ai Oct 16 '20 at 19:10

Why is my program saying that 5 * 5 is equal to 104126025?

1 Answers1