1045: [HAOI2008] 糖果传递

数学分析题，同UVA 11300。

lrj书上有详解。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=1000000+5;
int n,a[N],p[N];
typedef long long ll;
int abs(int x){
	return x>=0?x:-x;
}
inline int read(){
	int num=0;char ch;
	while(ch<'0'||ch>'9')ch=getchar();
	while(ch>='0'&&ch<='9'){num=num*10+ch-'0';ch=getchar();}
	return num;
}
int main(){
	ll avg=0,ans=0;
	n=read();for(int i=1;i<=n;i++){a[i]=read();avg+=a[i];}
	avg/=n;
	for(int i=2;i<=n;i++)p[i]=p[i-1]+a[i]-avg;
	sort(p+1,p+1+n);
	int mid=p[1+n>>1];
	for(int i=1;i<=n;i++)ans+=abs(p[i]-mid);
	printf("%lld",ans);
	return 0;
}