@0x0101

Firstly , startIndex = [0] not [1,0]

There is the vector constructor

vector (size_type n, const value_type& val,const allocator_type& alloc = allocator_type());
(just understand this )
vector (size_type n, const value_type& val...);

So vector<int> (1,0) just 1 elements(0) in the container = {0};

Secondly,We begin at the first elements in rings , it mean we start searching from index 0