用模拟退火写了 NOIP2021 方差，代码如下：

#include<bits/stdc++.h>
using namespace std;
#define N 10003
#define LL long long
#define INF 0x3f3f3f3f3f3f3f3f
int n,a[N],d[N];
LL ans=INF;
LL calc(){
	for(int i=1;i<=n;++i)
		a[i]=a[i-1]+d[i];
	LL pfh=0,hpf=0;
	for(int i=1;i<=n;++i)
		pfh+=a[i]*a[i],hpf+=a[i];
	return n*pfh-hpf*hpf;
}
void month(){
	LL lst=calc();
	ans=min(ans,lst);
	for(double t=1e3;t>1e-7;t*=0.99){
		LL llst=lst;
		int u=rand()%(n-1)+2,v=rand()%(n-1)+2;
		swap(d[u],d[v]);
		LL y=calc();
		ans=min(ans,y),lst=y;
		double del=y-llst;
		if(exp(-del/t)<(double)rand()/RAND_MAX)
			swap(d[u],d[v]),lst=llst;
	}
}
int main(){
	freopen("variance.in","r",stdin);
	freopen("variance.out","w",stdout);
	scanf("%d",&n);
	if(n==1) return puts("0"),0;
	srand(time(0));
	for(int i=1;i<=n;++i)
		scanf("%d",&a[i]),
		d[i]=a[i]-a[i-1];
	while((double)clock()/CLOCKS_PER_SEC<0.85)
		month();
	printf("%lld\n",ans);
	return 0;
}

windows 下能过编，交到洛谷也能正常评测（而且退了个 88pts），在自己电脑 Linux 模拟机上也没有任何问题，但是在我们教练的 Linux 评测机上 CE，这是为啥