[树状数组] poj 1990 MooFest

代码

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
#include<algorithm>
#include<map>
using namespace std;
const int maxn=2e4+5;
struct Cow
{
int v,p;
friend bool operator<(Cow x,Cow y)
{
if(x.v<y.v) return true;
if(x.v==y.v) return x.p<y.p;
return false;
}
}cow[maxn];
int n;
int num;
int maxb;
int bit[maxn],bitn[maxn];
inline int lowbit(int x){return x&-x;}
void add(int x)
{
for(int i=x;i<=maxb;i+=lowbit(i))
{
bit[i]+=x;
bitn[i]++;
}
}
long long getsum(int x)
{
long long res=0;
for(int i=x;i>0;i-=lowbit(i))
res+=bit[i];
return res;
}
long long getnum(int x)
{
long long res=0;
for(int i=x;i>0;i-=lowbit(i))
res+=bitn[i];
return res;
}
int main()
{
cin>>n;
maxb=-1;
memset(bit,0,sizeof bit);
memset(bitn,0,sizeof bitn);
for(int i=0;i<n;i++)
scanf("%d%d",&cow[i].v,&cow[i].p),
maxb=max(maxb,cow[i].p);
sort(cow,cow+n);
long long ans=0;
for(int i=0;i<n;i++)
{
num=getnum(cow[i].p);
ans+=(2*(num*cow[i].p-getsum(cow[i].p))+getsum(maxb)-i*cow[i].p)*cow[i].v;
add(cow[i].p);
}
cout<<ans<<endl;
return 0;
}