【bzoj4240】有趣的家庭菜园

#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<cmath>
using namespace std;
 
typedef long long LL;
 
#define lowbit(x) (x & (-x))
#define N 300010
 
struct Node
{
    int h,id;
}a[N];
 
int n;
int cnt;
LL ans;
 
int c[N];
 
int read()
{  
    int x=0; 
    char ch=getchar();  
    while (ch<‘0‘ || ch>‘9‘) 
        ch=getchar();  
    while (ch>=‘0‘ && ch<=‘9‘)
    {
        x=x*10+ch-‘0‘; 
        ch=getchar();
    }  
    return x;  
}  
 
bool cmp(Node x,Node y)
{
    return x.h>y.h;
}
 
void add(int x)
{
    while (x<=n)
        c[x]++,x+=lowbit(x);
}
 
int query(int x)
{
    int res(0);
    while (x)
        res+=c[x],x-=lowbit(x);
    return res;
}
 
int main()
{
    n=read();
    for (int i=1;i<=n;i++)
        a[i].h=read(),a[i].id=i;
    sort(a+1,a+n+1,cmp);
    int k=1;
    for (int i=1;i<=n;i++)
    {
        if (a[i].h!=a[i-1].h)
            while (k<i)
                add(a[k++].id);
        cnt=query(a[i].id);
        ans+=min(cnt,k-1-cnt);
    }
    printf("%lld",ans);
    return 0;
}