bzoj3192: [JLOI2013]删除物品（树状数组）

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#include<algorithm>
#define ll long long
using namespace std;
const int maxn=500010;
int n, m;
ll ans;
int a[maxn], b[maxn], pos[maxn], tree[maxn];
void read(int &k)
{
    int f=1; k=0; char c=getchar();
    while(c<‘0‘ || c>‘9‘) c==‘-‘ && (f=-1), c=getchar();
    while(c<=‘9‘ && c>=‘0‘) k=k*10+c-‘0‘, c=getchar();
    k*=f;
}
inline void add(int x, int delta){for(;x<=n;x+=x&-x) tree[x]+=delta;}
inline int query(int x){int sum=0; for(;x;x-=x&-x) sum+=tree[x]; return sum;}
int main()
{
    read(n); read(m);
    for(int i=n;i;i--) read(a[i]), b[i]=a[i];
    for(int i=n+1;i<=n+m;i++) read(a[i]), b[i]=a[i];
    n+=m; for(int i=1;i<=n;i++) tree[i]=i&-i;
    sort(b+1, b+1+n);
    for(int i=1;i<=n;i++) a[i]=lower_bound(b+1, b+1+n, a[i])-b;
    for(int i=1;i<=n;i++) pos[a[i]]=i;
    int now=n-m;
    for(int i=n;i;i--)
    {
        if(pos[i]>now) ans+=query(pos[i]-1)-query(now);
        else ans+=query(now)-query(pos[i]);
        add(pos[i], -1); now=pos[i];
    }
    printf("%lld\n", ans);
}