CodeForces 1093C Mishka and the Last Exam

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题意：

给定n/2个数，每个数拆分成两个数，将这两个数分别置于首尾（次首、次尾逐渐内缩）要求排列后这个序列是非递减的，要求你输出这个序列。

思路：
率先想到0 + a[i]，判断首尾是否满足条件，满足就插入，不满足就内缩。

Code

#include <bits/stdc++.h>

using namespace std;
typedef long long LL;
const LL maxn = 1e5+5;

LL a[maxn];
vector<LL> v;

int main()
{
	int n;
	cin >> n;
	for (int i = 0; i < n / 2; i++) cin >> a[i];
	v.push_back(0);
	v.push_back(a[0]);
	LL ps = 0, pe = a[0];
	for (int i = 1; i < n / 2; i++)
	{
		if (a[i] > pe)
		{
			LL pps = a[i] - pe;
			LL ppe = pe;

			if (pps < ps)
			{
				ppe -= (ps - pps);
				v.push_back(ps);
				v.push_back(ppe);
				pe = ppe;
			}
			else
			{
				v.push_back(pe);
				v.push_back(a[i] - pe);
				ps = a[i] - pe;
			}
		}
		else
		{
			if (0 < ps)
			{
				v.push_back(ps);
				v.push_back(a[i] - ps);
				pe = a[i] - ps;
			}
			else
			{
				v.push_back(0);
				v.push_back(a[i]);
				pe = a[i];
			}
		}
	}
	sort(v.begin(), v.end());
	for (int i = 0; i < v.size(); i++)
	{
		if (i) cout << " ";
		cout << v[i];
	}
	cout << endl;
	return 0;
}