# stable_partition

Classifies elements in a range into two disjoint sets, with those elements satisfying a unary predicate preceding those that fail to satisfy it, preserving the relative order of equivalent elements.

```
template<class BidirectionalIterator, class Predicate>
BidirectionalIterator stable_partition(
BidirectionalIterator _First,
BidirectionalIterator _Last,
Predicate _Pred
);
```

## Parameters

_First

A bidirectional iterator addressing the position of the first element in the range to be partitioned._Last

A bidirectional iterator addressing the position one past the final element in the range to be partitioned._Pred

User-defined predicate function object that defines the condition to be satisfied if an element is to be classified. A predicate takes single argument and returns**true**or**false**.

## Return Value

A bidirectional iterator addressing the position of the first element in the range to not satisfy the predicate condition.

## Remarks

The range referenced must be valid; all pointers must be dereferenceable and within the sequence the last position is reachable from the first by incrementation.

Elements *a* and *b* are equivalent, but not necessarily equal, if both *Pr* (*a*, *b*) is false and *Pr* (*b*, *a*) if false, where *Pr* is the parameter-specified predicate. The **stable_ partition** algorithm is stable and guarantees that the relative ordering of equivalent elements will be preserved. The algorithm **partition** does not necessarily preserve this original ordering.

## Example

```
// alg_stable_partition.cpp
// compile with: /EHsc
#include <vector>
#include <algorithm>
#include <iostream>
bool greater5 ( int value ) {
return value >5;
}
int main( ) {
using namespace std;
vector <int> v1, v2;
vector <int>::iterator Iter1, Iter2, result;
int i;
for ( i = 0 ; i <= 10 ; i++ )
v1.push_back( i );
int ii;
for ( ii = 0 ; ii <= 4 ; ii++ )
v1.push_back( 5 );
random_shuffle(v1.begin( ), v1.end( ) );
cout << "Vector v1 is ( " ;
for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
cout << *Iter1 << " ";
cout << ")." << endl;
// Partition the range with predicate greater10
result = stable_partition (v1.begin( ), v1.end( ), greater5 );
cout << "The partitioned set of elements in v1 is:\n ( " ;
for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
cout << *Iter1 << " ";
cout << ")." << endl;
cout << "The first element in v1 to fail to satisfy the"
<< "\n predicate greater5 is: " << *result << "." << endl;
}
```

## Sample Output

```
Vector v1 is ( 5 1 9 2 0 5 7 3 4 5 8 5 5 5 10 6 ).
The partitioned set of elements in v1 is:
( 9 7 8 10 6 5 1 2 0 5 3 4 5 5 5 5 ).
The first element in v1 to fail to satisfy the
predicate greater5 is: 5.
```

## Requirements

**Header:** <algorithm>

**Namespace:** std