std::stable_partition (3) - Linux Manuals

std::stable_partition: std::stable_partition

NAME

std::stable_partition - std::stable_partition

Synopsis

Defined in header <algorithm>
template< class BidirIt, class UnaryPredicate > (1)
BidirIt stable_partition( BidirIt first, BidirIt last, UnaryPredicate p );
template< class ExecutionPolicy, class BidirIt, class UnaryPredicate > (2) (since C++17)
BidirIt stable_partition( ExecutionPolicy&& policy, BidirIt first, BidirIt last, UnaryPredicate p );

1) Reorders the elements in the range [first, last) in such a way that all elements for which the predicate p returns true precede the elements for which predicate p returns false. Relative order of the elements is preserved.
2) Same as (1), but executed according to policy. This overload only participates in overload resolution if std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true.

Parameters

first, last - the range of elements to reorder
policy - the execution policy to use. See execution_policy for details.
              unary predicate which returns true if the element should be ordered before other elements.
p - The expression p(v) must be convertible to bool for every argument v of type (possibly const) VT, where VT is the value type of BidirIt, regardless of value_category, and must not modify v. Thus, a parameter type of VT&is not allowed
              , nor is VT unless for VT a move is equivalent to a copy
              (since C++11).

Type requirements

-
BidirIt must meet the requirements of ValueSwappable and LegacyBidirectionalIterator.
-
The type of dereferenced BidirIt must meet the requirements of MoveAssignable and MoveConstructible.
-
UnaryPredicate must meet the requirements of Predicate.

Return value

Iterator to the first element of the second group

Complexity

Given N = last - first
1) Exactly N applications of the predicate and O(N) swaps if there is enough extra memory. If memory is insufficient, at most N log N swaps.
2) O(N log N) swaps and O(N) applications of the predicate

Exceptions

The overload with a template parameter named ExecutionPolicy reports errors as follows:

* If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard_policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
* If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Notes

This function attempts to allocate a temporary buffer. If the allocation fails, the less efficient algorithm is chosen.

Example

// Run this code

  #include <iostream>
  #include <algorithm>
  #include <vector>

  int main()
  {
      std::vector<int> v{0, 0, 3, 0, 2, 4, 5, 0, 7};
      std::stable_partition(v.begin(), v.end(), [](int n){return n>0;});
      for (int n : v) {
          std::cout << n << ' ';
      }
      std::cout << '\n';
  }

Output:

  3 2 4 5 7 0 0 0 0