bzoj1901: Zju2112 Dynamic Rankings 主席树+树状数组

主席树+树状数组求带修改的区间第k大

#include<bits/stdc++.h>
using namespace std;
int n,m,root[200100],q1[100000],q2[100000],tot=0,dd,len=0,a[100010],hash[200010],sum[5001000],l[5010000],r[5010000],b[1000100],c[1000010],d[1000010];
char s[10010];
int lowbit(int pp)
{return pp&(-pp);}
void update(int &rt,int L,int R,int x,int val)
{
    if(!rt)rt=++len;
    sum[rt]+=val;
    if(L<R)
    {
        int mid=(L+R)>>1;
        if(x<=mid)update(l[rt],L,mid,x,val);
        else update(r[rt],mid+1,R,x,val);
    }
}
int main()
{
    //freopen("xf.in","r",stdin);
    //freopen("xf.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
        hash[++tot]=a[i];
    }
    for(int i=1;i<=m;i++)
    {
        cin>>s[i];
        if(s[i]=='Q')scanf("%d%d%d",&b[i],&c[i],&d[i]);
        else {scanf("%d%d",&b[i],&c[i]);hash[++tot]=c[i];}
    }
    sort(hash+1,hash+tot+1);
    dd=unique(hash+1,hash+tot+1)-hash-1;
    for(int i=1;i<=n;i++)
    {
        int x=lower_bound(hash+1,hash+dd+1,a[i])-hash;
        for(int j=i;j<=n;j+=lowbit(j))update(root[j],1,dd,x,1);
    }
    for(int i=1;i<=m;i++)
    {
        if(s[i]=='Q')
        {
            int xx=b[i]-1,yy=c[i],L=1,R=dd;
            int x=d[i];
            int tail1=0,tail2=0;
            while(xx)
                {
                    q1[++tail1]=root[xx];xx-=lowbit(xx);
                }
                while(yy)
                {
                    q2[++tail2]=root[yy];yy-=lowbit(yy);
                }
            while(L<R)
            {
                  
                int ans=0;
                for(int j=1;j<=tail1;j++)ans-=sum[l[q1[j]]];
                for(int j=1;j<=tail2;j++)ans+=sum[l[q2[j]]];
                int mid=(L+R)>>1;
                if(x<=ans)
                {
                    R=mid;
                      
                    for(int j=1;j<=tail1;j++)
                        q1[j]=l[q1[j]];
                    for(int j=1;j<=tail2;j++)
                        q2[j]=l[q2[j]];
                }
                else
                {
                    L=mid+1;
                    x-=ans;
                    for(int j=1;j<=tail1;j++)
                        q1[j]=r[q1[j]];
                    for(int j=1;j<=tail2;j++)
                        q2[j]=r[q2[j]];
                }
            }
            printf("%d\n",hash[L]);
        }
        else
        {
            int x=lower_bound(hash+1,hash+dd+1,a[b[i]])-hash;
            for(int j=b[i];j<=n;j+=lowbit(j))update(root[j],1,dd,x,-1);
            x=lower_bound(hash+1,hash+dd+1,c[i])-hash;
            for(int j=b[i];j<=n;j+=lowbit(j))update(root[j],1,dd,x,1);
            a[b[i]]=c[i];
        }
    }
    return 0;
}