BZOJ3850: ZCC Loves Codefires

题目：http://www.lydsy.com/JudgeOnline/problem.php?id=3850

题解：类似于国王游戏，推一下相邻两个元素交换的条件然后排个序就可以了。

代码：

#include<cstdio>

#include<cstdlib>

#include<cmath>

#include<cstring>

#include<algorithm>

#include<iostream>

#include<vector>

#include<map>

#include<set>

#include<queue>

#include<string>

#define inf 1000000000

#define maxn 200000+5

#define maxm 200000+5

#define eps 1e-10

#define ll long long

#define pa pair<int,int>

#define for0(i,n) for(int i=0;i<=(n);i++)

#define for1(i,n) for(int i=1;i<=(n);i++)

#define for2(i,x,y) for(int i=(x);i<=(y);i++)

#define for3(i,x,y) for(int i=(x);i>=(y);i--)

#define for4(i,x) for(int i=head[x],y=e[i].go;i;i=e[i].next,y=e[i].go)

#define for5(n,m) for(int i=1;i<=n;i++)for(int j=1;j<=m;j++)

#define mod 1000000007

using namespace std;

inline int read()

{

    int x=0,f=1;char ch=getchar();

    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}

    while(ch>='0'&&ch<='9'){x=10*x+ch-'0';ch=getchar();}

    return x*f;

}
struct rec{int x,y;}a[maxn];
int n;
inline bool cmp(rec a,rec b){return a.x*b.y<b.x*a.y;}

int main()

{

    freopen("input.txt","r",stdin);

    freopen("output.txt","w",stdout);

    n=read();
    for1(i,n)a[i].x=read();
    for1(i,n)a[i].y=read();
    sort(a+1,a+n+1,cmp);
    ll ans=0,sum=0;
    for1(i,n)
    {
        sum+=a[i].x;
        ans+=sum*(ll)a[i].y;
    }
    cout<<ans<<endl;

    return 0;

}