求助大佬！！谢谢！

#include<bits/stdc++.h>
#define ll long long
using namespace std;

const ll MAX=1e6+5;

struct node{
    ll num;//编号 
    ll v;//权值 
}f[MAX];

ll n;//n个数 
ll ans;//逆序对个数 
ll c[MAX];//树状数组 

int getsum(int i){
    int s=0;
    while(i) s+=c[i],i-=i&(-i);
    return s;
}//求和 

inline void updata(int i){ while(i<=n) c[i]++,i+=i&(-i);}//c[i]的改变值值为1

inline bool cmp(node x,node y){ return x.v>y.v;}

inline ll read(){
    int x=0,f=1; char c=getchar();
    while(c<'0'||c>'9'){ if(c=='-') f=-1; c=getchar();}
    while(c>='0'&&c<='9'){ x=(x<<1)+(x<<3)+(c^48); c=getchar();}
    return x*f;
}

int main(){

    n=read();
    for(register ll i=1;i<=n;i++) f[i].v=read(),f[i].num=i;

    sort(1+f,1+n+f,cmp);//排序(按权值大-->小)

    for(register ll i=1;i<=n;i++){
        updata(f[i].num);
        ans+=getsum(f[i].num);//我的逆序对有哪些 
    }

    printf("%lld",ans);

    return 0;
}