Defined in header <algorithm>  

template< class BidirIt, class UnaryPredicate > BidirIt stable_partition( BidirIt first, BidirIt last, UnaryPredicate p );  (1)  
template< class ExecutionPolicy, class BidirIt, class UnaryPredicate > BidirIt stable_partition( ExecutionPolicy&& policy, BidirIt first, BidirIt last, UnaryPredicate p );  (2)  (since C++17) 
[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. policy
. This overload does not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>
(until C++20) std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>
(since C++20) is true.first, last    the range of elements to reorder 
policy    the execution policy to use. See execution policy for details. 
p    unary predicate which returns true if the element should be ordered before other elements. The expression 
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. 
Iterator to the first element of the second group.
Given N = std::distance(first, last)
,
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.O(N log N)
swaps and O(N)
applications of the predicateThe overload with a template parameter named ExecutionPolicy
reports errors as follows:
ExecutionPolicy
is one of the standard policies, std::terminate
is called. For any other ExecutionPolicy
, the behavior is implementationdefined. std::bad_alloc
is thrown. This function attempts to allocate a temporary buffer. If the allocation fails, the less efficient algorithm is chosen.
Implementations in libc++ and libstdc++ also accept ranges denoted by LegacyForwardIterators as an extension.
#include <iostream> #include <algorithm> #include <vector> int main() { std::vector<int> v{0, 0, 3, 1, 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 1 0
divides a range of elements into two groups (function template) 

(C++20)  divides elements into two groups while preserving their relative order (niebloid) 
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