bzoj3192 [JLOI2013]删除物品

　　用数组表示两个栈，将两个栈的栈顶并在一起，用树状数组维护一下操作即可。

　　代码

#include<cstdio>
#include<algorithm>
#include<map>
#define lb(x) (x&-x)
using namespace std;
const int N = 501010;
int n,m,i,id[N],a[N],b[N],c[N],top,tot;
long long ans;
map<int,int> ma;
void cc(int x,int w)
{
    while (x<=n+m)
    {
        c[x]+=w;
        x+=lb(x);
    }
}
int sum(int x)
{
    int ans=0;
    while (x)
    {
        ans+=c[x];
        x-=lb(x);
    }
    return ans;
}
int main()
{
    scanf("%d%d",&n,&m);
    for (i=1;i<=n;i++)
    scanf("%d",&a[i]),b[i]=a[i];
    for (i=n+1;i<=n+m;i++)
    scanf("%d",&a[i]),b[i]=a[i];
    sort(b+1,b+1+m+n);
    for (i=1;i<=n+m;i++) 
    if (ma[b[i]]==0) ma[b[i]]=++tot;
    for (i=1;i<=n+m;i++) a[i]=ma[a[i]];
    for (i=1;i<=n;i++)
        id[a[i]]=n-i+1;
    for (i=1;i<=m;i++)
        id[a[n+i]]=n+i;
    
    for (i=1;i<=n+m;i++) cc(i,1);
    
    top=n;
    for (i=n+m;i>=1;i--)
    {
        if (id[i]<=top)
        {
        ans+=sum(top)-sum(id[i]);
        top=id[i];
        }
        else
        {
        ans+=sum(id[i]-1)-sum(top);
        top=id[i];
        }
        cc(id[i],-1);
    }
    printf("%lld
",ans);
}