Aquileo | std::stable_partition in C++

stable_partition() rearranges elements in a container so that those satisfying a given condition come first, while preserving their original order.

It’s called stable because it keeps the relative order of elements the same within each group.
It divides elements in a container (like an array or vector) into two groups based on a given condition .
The syntax of std::stable_sort is std::stable_sort(first, last, comp), where first and last specify the range of elements to be sorted, and comp is an optional comparison function that determines the sorting order.
It is present in <algorithm> header file.

C++

#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
int main()
{
    vector<int> v{6, 9, 0, 1, 2, 7, 5, 8, 0};
    stable_partition(v.begin(), v.end(), [](int n) { return n > 0; });
    for (int n : v)
    {
        cout << n << ' ';
    }
    cout << '\n';
}

Output

6 9 1 2 7 5 8 0 0

CPP

#include <algorithm> // For stable_partition
#include <iostream>
#include <vector>
using namespace std;

bool odd(int i)
{
    return (i % 2) == 1;
}

int main()
{
    vector<int> vct;

    // Fill vector with numbers 1 to 9
    for (int i = 1; i < 10; ++i)
        vct.push_back(i); // 1 2 3 4 5 6 7 8 9

    // Rearrange elements so that odd numbers come first
    auto bound = stable_partition(vct.begin(), vct.end(), odd);

    cout << "Odd numbers:";
    for (auto it = vct.begin(); it != bound; ++it)
        cout << ' ' << *it;
    cout << '\n';

    cout << "Even numbers:";
    for (auto it = bound; it != vct.end(); ++it)
        cout << ' ' << *it;
    cout << '\n';

    return 0;
}

Output:

odd numbers: 1 3 5 7 9
even numbers: 2 4 6 8

std::stable_partition in C++

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