【COGS 741】[网络流24题] 负载平衡

题目传送门：http://cojs.tk/cogs/problem/problem.php?pid=741

虽然是“网络流24题”之一，然而可以O(n)搞
来来来，我们一起来推式子！
6541324587

#include<bits/stdc++.h>
using namespace std;

const int N = 100+9;

int n,arr[N],sum,vout,sta;

inline int read(){
	char c=getchar(); int ret = 0, f = 1;
	while (c<'0'||c>'9') {if(c=='-')f=-1;c=getchar();}
	while (c<='9'&&c>='0') {ret=ret*10+c-'0';c=getchar();}
	return ret*f;
}

int main(){
	freopen("overload.in","r",stdin);
	freopen("overload.out","w",stdout);
	n = read(); 
	for (int i=1;i<=n;i++) sum += (arr[i] = read()); sum /= n;
	for (int i=1;i<=n;i++) arr[i] -= sum - arr[i-1];
	nth_element(arr+1,arr+n/2,arr+n); sta=arr[n/2];
	for (int i=1;i<=n;i++) vout += abs(arr[i]-sta);
	cout<<vout<<endl;  
	return 0;
} 

感觉真的是好神奇啊！