C++ Brain Teasers

Puzzle 19

A Little Sum Thing

a-little-sum-thing.cpp

#include <iostream>
#include <numeric>
#include <vector>

int main()
{
    std::vector<int> v{-2, -3};
    std::cout << std::accumulate(v.cbegin(), v.cend(), v.size());
}

Guess the Output
	Try to guess what the output is before moving to the next page.

The program has implementation-defined behavior! But it outputs a large number, like this one for instance:

18446744073709551613