CTPAS
asked on
What is the output of this sort function?
IF
vector<int> A; // 10 elements, say 0-9
vector<long> B; // 10 elements, say all == 1
AND
struct SPredicate
{
const long* _rowBegin;
SPredicate(const vector<long>& v) : _rowBegin( v.begin() ) { }
bool operator()(int i, int j) { return _rowBegin[ i ] < _rowBegin[ j ] ; }
};
What would the ouput be of the following?
std::sort(A.begin(), A.end(),SPredicate(B));
vector<int> A; // 10 elements, say 0-9
vector<long> B; // 10 elements, say all == 1
AND
struct SPredicate
{
const long* _rowBegin;
SPredicate(const vector<long>& v) : _rowBegin( v.begin() ) { }
bool operator()(int i, int j) { return _rowBegin[ i ] < _rowBegin[ j ] ; }
};
What would the ouput be of the following?
std::sort(A.begin(), A.end(),SPredicate(B));
evilrix
The predicate is indexing B and comparing B using the current value of i and j (both of which will be values of A); however, all elements in B are 1 so I'd expect that A would remain in the same order as it was initially.
^^^this assumes that the iterator of a vector is convertible to a type T *, which the C++ Standard doesn't as far as I can remember, define.
ASKER
Thanks for quick resonse
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ASKER
yes. I was only unclear about where i , j came from in the comparison.
This method is a compact way to order set A elements based on the ordering of set B
This method is a compact way to order set A elements based on the ordering of set B