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=,f=;char ch=getchar();

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

     while(ch>=''&&ch<=''){x=*x+ch-'';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+,a+n+,cmp);
     ll ans=,sum=;
     for1(i,n)
     {
         sum+=a[i].x;
         ans+=sum*(ll)a[i].y;
     }
     cout<<ans<<endl;

     return ;

 }