This can be solved using a variation on the usual erase-remove idiom, with a lambda inside the std::remove_if
that looks up the index of the current row inside an iterator range of to be removed indices:
#include <algorithm> // find, remove_if
#include <iostream>
#include <vector>
template<class T>
using M = std::vector<std::vector<T>>; // matrix
template<class T>
std::ostream& operator<<(std::ostream& os, M<T> const& m)
{
for (auto const& row : m) {
for (auto const& elem : row)
os << elem << " ";
os << "\n";
}
return os;
}
template<class T, class IdxIt>
void erase_rows(M<T>& m, IdxIt first, IdxIt last)
{
m.erase(
std::remove_if(
begin(m), end(m), [&](auto& row) {
auto const row_idx = &row - &m[0];
return std::find(first, last, row_idx) != last;
}),
end(m)
);
}
int main()
{
auto m = M<int> { { 0, 1, 2, 3 }, { 3, 4, 5, 6 }, { 6, 7, 8, 9 }, { 1, 0, 1, 0 } };
std::cout << m << "\n";
auto drop = { 1, 3 };
erase_rows(m, begin(drop), end(drop));
std::cout << m << "\n";
}
Note: because from C++11 onwards, std::vector
has move semantics, shuffling rows around in your std::vector<std::vector<T>>
is done using simple pointer manipulations, regardless of your type T
(it would be quite different if you want column-deletion, though!).