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To: ALT Linux Community general discussions <community@lists.altlinux.org>
From: Pavel Vainerman <pv@etersoft.ru>
Message-ID: <101a26f1-1b29-ca8d-c1f3-d86b8797ef91@etersoft.ru>
Date: Fri, 25 Aug 2017 01:13:08 +0300
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Добрый день.

Обнаружил тут странное поведение у std::partition().
Вот тестовый код (c++11).

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

using namespace std;

void print( vector<int>& v )
{
	for( const auto& i: v )
		cout << setw(3) << i;
	cout << endl;
}

int main()
{
	vector<int> v =  { -10, 0, -4, 5, -2 , 0, 3, 1, 7, 8, 9 };

	print(v);
	std::partition(v.begin(),v.end(),[](int v){ return v<0; });
	print(v);

	return 0;
}

Вот результат (первая строка, исходный вектор, вторая преобразованный,
опорный элемент 0).

-10  0 -4  5 -2  0  3  1  7  8  9
-10 -2 -4  5  0  0  3  1  7  8  9

Так вот смущает меня почему "5" не правее нулей?
Может ли кто-нибудь пояснить, почему так?


-- 
Pavel Vainerman
www.etersoft.ru