BZOJ 1901 Zju2112 Dynamic Rankings 题解

  1 #include<cstdio>
  2 #include<algorithm>
  3 const int MAXN=10000+5;
  4 const int INF=~0U>>1;
  5 const int BUFFER_SIZE=10000;
  6 const int MAXM=10000+5;
  7 struct Tree{
  8     Tree* pl,*pr;
  9     int l,r,sum;
 10     Tree* set(int _l,int _r,Tree* _pl,Tree* _pr)
 11     {
 12         l=_l;r=_r;pl=_pl;pr=_pr;
 13         sum=pl->sum+pr->sum;
 14         return this;
 15     }
 16     Tree* set(int _l,int _r,int all);
 17     Tree* add(int pos,int ad);
 18 };
 19 Tree* buffer=0,*cur;
 20 inline Tree* get()
 21 {
 22     if(!buffer || cur-buffer==BUFFER_SIZE)
 23         buffer=new Tree[BUFFER_SIZE],cur=buffer;
 24     return cur++;
 25 }
 26 Tree* Tree::set(int _l,int _r,int all)
 27 {
 28     l=_l;r=_r;
 29     if(l+1==r) sum=all;
 30     else
 31     {
 32         int m=(l+r)>>1;
 33         pl=get()->set(l,m,all);
 34         pr=get()->set(m,r,all);
 35         sum=pl->sum+pr->sum;
 36     }
 37     return this;
 38 }
 39 Tree* Tree::add(int pos,int ad)
 40 {
 41     if(l+1==r) return get()->set(l,r,sum+ad);
 42     int m=(l+r)>>1;
 43     if(pos<m) return get()->set(l,r,pl->add(pos,ad),pr);
 44     else return get()->set(l,r,pl,pr->add(pos,ad));
 45 }
 46 inline int lowbit(int x)
 47 {    return x&-x;    }
 48 int n,m;
 49 Tree* root[MAXN];
 50 void update(int x,int pos,int ad)
 51 {
 52     for(;x<=n;x+=lowbit(x))
 53         root[x]=root[x]->add(pos,ad);
 54 }
 55 Tree* ptl[MAXN],*ptr[MAXN];
 56 int lnum,rnum;
 57 inline void get_trees(int x,int y)
 58 {
 59     lnum=rnum=0;
 60     for(;x>0;x-=lowbit(x))
 61         ptl[lnum++]=root[x];
 62     for(;y>0;y-=lowbit(y))
 63         ptr[rnum++]=root[y];
 64 }
 65 inline int get_sum()
 66 {
 67     int cnt1=0,cnt2=0;
 68     for(int i=0;i<lnum;++i) cnt1+=ptl[i]->pl->sum;
 69     for(int i=0;i<rnum;++i) cnt2+=ptr[i]->pl->sum;
 70     return cnt2-cnt1;
 71 }
 72 inline int query(int x,int y,int k)
 73 {
 74     get_trees(x-1,y);
 75     while(ptr[0]->l +1 < ptr[0]->r)
 76     {
 77         int cnt=get_sum();
 78         if(cnt<=k)
 79         {
 80             k-=cnt;
 81             for(int i=0;i<lnum;++i) ptl[i]=ptl[i]->pr;
 82             for(int i=0;i<rnum;++i) ptr[i]=ptr[i]->pr;
 83         }
 84         else
 85         {
 86             for(int i=0;i<lnum;++i) ptl[i]=ptl[i]->pl;
 87             for(int i=0;i<rnum;++i) ptr[i]=ptr[i]->pl;
 88         }
 89     }
 90     return ptr[0]->l;
 91 }
 92 struct Ask{
 93     int kind,a,b,c;
 94 }ask[MAXM];
 95 int w[MAXN],sortw[MAXN+MAXM];
 96 int main()
 97 {
 98     freopen("1.in","r",stdin);
 99     scanf("%d%d",&n,&m);
100     int p;
101     for(int i=0;i<n;++i)
102         scanf("%d",w+i),sortw[i]=w[i];
103     p=n;
104     char cmd[5];
105     for(int i=0;i<m;++i)
106     {
107         scanf("%s",cmd);
108         if(cmd[0]==‘Q‘)
109         {
110             ask[i].kind=0;
111             scanf("%d%d%d",&ask[i].a,&ask[i].b,&ask[i].c);
112         }
113         else
114         {
115             ask[i].kind=1;
116             scanf("%d%d",&ask[i].a,&ask[i].b);
117             sortw[p]=ask[i].b;
118             p++;
119         }
120     }
121     std::sort(sortw,sortw+p);
122     int nn=std::unique(sortw,sortw+p)-sortw;
123     for(int i=0;i<n;++i) w[i]=std::lower_bound(sortw,sortw+nn,w[i])-sortw;
124     root[0]=get()->set(0,nn,0);
125     for(int i=1;i<=n;++i) root[i]=root[0]->add(w[i-1],1);
126     for(int i=1;i<=n;++i) update(i+lowbit(i),w[i-1],1);
127     for(int i=0;i<m;++i)
128     {
129         if(!ask[i].kind) printf("%d\n",sortw[query(ask[i].a,ask[i].b,ask[i].c-1)]);
130         else
131         {
132             int t=std::lower_bound(sortw,sortw+nn,ask[i].b)-sortw;
133             update(ask[i].a,w[ask[i].a-1],-1);
134             w[ask[i].a-1]=t;
135             update(ask[i].a,t,1);
136         }
137     }
138     return 0;
139 }