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：
1 #include<cstdio> 2 3 #include<cstdlib> 4 5 #include<cmath> 6 7 #include<cstring> 8 9 #include<algorithm> 10 11 #include<iostream> 12 13 #include<vector> 14 15 #include<map> 16 17 #include<set> 18 19 #include<queue> 20 21 #include<string> 22 23 #define inf 1000000000 24 25 #define maxn 200000+5 26 27 #define maxm 200000+5 28 29 #define eps 1e-10 30 31 #define ll long long 32 33 #define pa pair<int,int> 34 35 #define for0(i,n) for(int i=0;i<=(n);i++) 36 37 #define for1(i,n) for(int i=1;i<=(n);i++) 38 39 #define for2(i,x,y) for(int i=(x);i<=(y);i++) 40 41 #define for3(i,x,y) for(int i=(x);i>=(y);i--) 42 43 #define for4(i,x) for(int i=head[x],y=e[i].go;i;i=e[i].next,y=e[i].go) 44 45 #define for5(n,m) for(int i=1;i<=n;i++)for(int j=1;j<=m;j++) 46 47 #define mod 1000000007 48 49 using namespace std; 50 51 inline int read() 52 53 { 54 55 int x=0,f=1;char ch=getchar(); 56 57 while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} 58 59 while(ch>='0'&&ch<='9'){x=10*x+ch-'0';ch=getchar();} 60 61 return x*f; 62 63 } 64 struct rec{int x,y;}a[maxn]; 65 int n; 66 inline bool cmp(rec a,rec b){return a.x*b.y<b.x*a.y;} 67 68 int main() 69 70 { 71 72 freopen("input.txt","r",stdin); 73 74 freopen("output.txt","w",stdout); 75 76 n=read(); 77 for1(i,n)a[i].x=read(); 78 for1(i,n)a[i].y=read(); 79 sort(a+1,a+n+1,cmp); 80 ll ans=0,sum=0; 81 for1(i,n) 82 { 83 sum+=a[i].x; 84 ans+=sum*(ll)a[i].y; 85 } 86 cout<<ans<<endl; 87 88 return 0; 89 90 }