std::erase_if (std::unordered_multimap)
From cppreference.com
< cpp | container | unordered multimap
Defined in header <unordered_map> | ||
template<class Key, class T, class Hash, class KeyEqual, class Alloc, class Pred > | (since C++20) | |
Erases all elements that satisfy the predicate pred from c.
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();
Contents |
[edit]Parameters
| c | - | container from which to erase |
| pred | - | predicate that returns true if the element should be erased |
[edit]Return value
The number of erased elements.
[edit]Complexity
Linear.
[edit]Example
Run this code
#include <iostream>#include <unordered_map> void println(auto rem, autoconst& container){std::cout<< rem <<'{';for(char sep[]{0, ' ', 0};constauto&[key, value]: container)std::cout<< sep <<'{'<< key <<", "<< value <<'}', *sep =',';std::cout<<"}\n";} int main(){std::unordered_multimap<int, char> data {{1, 'a'}, {2, 'b'}, {3, 'c'}, {4, 'd'}, {5, 'e'}, {4, 'f'}, {5, 'g'}, {5, 'g'}, }; println("Original:\n", data); constauto count =std::erase_if(data, [](constauto& item){autoconst&[key, value]= item;return(key &1)==1;}); println("Erase items with odd keys:\n", data);std::cout<< count <<" items removed.\n";}
Possible output:
Original: {{5, g}, {5, g}, {5, e}, {4, f}, {4, d}, {3, c}, {2, b}, {1, a}} Erase items with odd keys: {{4, f}, {4, d}, {2, b}} 5 items removed.[edit]See also
| removes elements satisfying specific criteria (function template) | |
(C++20)(C++20) | removes elements satisfying specific criteria (algorithm function object) |
