Difference between revisions of "cpp/container/vector/erase2"
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Revision as of 06:00, 6 November 2021
| Defined in header <vector>
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| (1) | ||
template< class T, class Alloc, class U > constexpr std::vector<T, Alloc>::size_type |
(since C++20) (until C++26) |
|
| template< class T, class Alloc, class U = T > constexpr std::vector<T, Alloc>::size_type |
(since C++26) | |
| template< class T, class Alloc, class Pred > constexpr std::vector<T, Alloc>::size_type |
(2) | (since C++20) |
1) Erases all elements that compare equal to value from the container. Equivalent to
auto it = std::remove(c.begin(), c.end(), value); auto r = c.end() - it; c.erase(it, c.end()); return r;
2) Erases all elements that satisfy the predicate pred from the container. Equivalent to
auto it = std::remove_if(c.begin(), c.end(), pred); auto r = c.end() - it; c.erase(it, c.end()); return r;
Contents |
Parameters
| c | - | container from which to erase |
| value | - | value to be removed |
| pred | - | unary predicate which returns true if the element should be erased. The expression pred(v) must be convertible to bool for every argument |
Return value
The number of erased elements.
Complexity
Linear.
Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_algorithm_default_value_type |
202403 | (C++26) | List-initialization for algorithm (1) |
Example
Run this code
#include <complex> #include <iostream> #include <numeric> #include <string_view> #include <vector> void println(std::string_view comment, const auto& c) { std::cout << comment << '['; bool first{true}; for (const auto& x : c) std::cout << (first ? first = false, "" : ", ") << x; std::cout << "]\n"; } int main() { std::vector<char> cnt(10); std::iota(cnt.begin(), cnt.end(), '0'); println("Initially, cnt = ", cnt); std::erase(cnt, '3'); println("After erase '3', cnt = ", cnt); auto erased = std::erase_if(cnt, [](char x) { return (x - '0') % 2 == 0; }); println("After erase all even numbers, cnt = ", cnt); std::cout << "Erased even numbers: " << erased << '\n'; std::vector<std::complex<double>> nums{{2, 2}, {4, 2}, {4, 8}, {4, 2}}; #ifdef __cpp_lib_algorithm_default_value_type std::erase(nums, {4, 2}); #else std::erase(nums, std::complex<double>{4, 2}); #endif println("After erase {4, 2}, nums = ", nums); }
Output:
Initially, cnt = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
After erase '3', cnt = [0, 1, 2, 4, 5, 6, 7, 8, 9]
After erase all even numbers, cnt = [1, 5, 7, 9]
Erased even numbers: 5
After erase {4, 2}, nums = [(2,2), (4,8)]See also
| removes elements satisfying specific criteria (function template) | |
| (C++20)(C++20) |
removes elements satisfying specific criteria (niebloid) |
