A1113 Integer Set Partition

#include<iostream>
#include<vector>
#include<map>
#include<string>
#include<cstring>
#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn = 100001;
int a[maxn];
int main()
{
	int n, s1 = 0, s2 = 0;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> a[i];
	}
	sort(a, a + n);
	for (int i = 0; i < n; i++)
	{
		if (i < n / 2) s1 += a[i];
		else s2 += a[i];
	}
	cout << n % 2 << " " << s2 - s1 << endl;
}

快排的Partition
据说复杂度可以降到O（n）结果有个点超时了。

#include<iostream>
#include<vector>
#include<map>
#include<string>
#include<cstring>
#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn = 100001;
int a[maxn];
int Kth_elem(int a[], int low, int high, int k) {
	swap(a[low], a[(low + high) / 2]);
	int pivot = a[low];
	int low_temp = low, high_temp = high;
	while (low < high) {
		while (low < high && a[high] >= pivot) high--;
		a[low] = a[high];
		while (low < high && a[low] <= pivot) low++;
		a[high] = a[low];
	}
	a[low] = pivot;
	if (low == k) return a[low];
	else if (low > k)
		return Kth_elem(a, low_temp, low - 1, k);
	else return Kth_elem(a, low + 1, high_temp, k);
}

int main()
{
	int n, s1 = 0, s2 = 0;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> a[i];
	}
	Kth_elem(a, 0, n - 1, n / 2);
	for (int i = 0; i < n; i++)
	{
		if (i < n / 2) s1 += a[i];
		else s2 += a[i];
	}
	cout << n % 2 << " " << s2 - s1 << endl;
}