std::erase_if (std::map)
Defined in header <map> |
||
|---|---|---|
|
(since C++20) |
Erases all elements that satisfy the predicate pred from the container. Equivalent to
auto old_size = c.size();
for (auto first = c.begin(), last = c.end(); first != last;)
{
if (pred(*first))
first = c.erase(first);
else
++first;
}
return old_size - c.size();Parameters
| c | - | container from which to erase |
| pred | - | predicate that returns true if the element should be erased |
Return value
The number of erased elements.
Complexity
Linear.
Example
#include <iostream>
#include <map>
void print(auto rem, auto const& container)
{
std::cout << rem << '{';
for (char sep[]{0, ' ', 0}; const auto& [key, value] : container)
std::cout << sep << '{' << key << ", " << value << '}', *sep = ',';
std::cout << "}\n";
}
int main()
{
std::map<int, char> data
{
{1, 'a'}, {2, 'b'}, {3, 'c'}, {4, 'd'},
{5, 'e'}, {4, 'f'}, {5, 'g'}, {5, 'g'},
};
print("Original:\n", data);
const auto count = std::erase_if(data, [](const auto& item)
{
auto const& [key, value] = item;
return (key & 1) == 1;
});
print("Erase items with odd keys:\n", data);
std::cout << count << " items removed.\n";
}Output:
Original:
{{1, a}, {2, b}, {3, c}, {4, d}, {5, e}}
Erase items with odd keys:
{{2, b}, {4, d}}
3 items removed.See also
| removes elements satisfying specific criteria (function template) |
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