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「bzoj3324」普通平衡树 - 替罪羊树 | Bill Yang's Blog

路终会有尽头,但视野总能看到更远的地方。

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「bzoj3324」普通平衡树 - 替罪羊树

题目大意

    您需要写一种数据结构(可参考题目标题),来维护一些数,其中需要提供以下操作:
    $1$. 插入$x$数
    $2$. 删除$x$数(若有多个相同的数,因只删除一个)
    $3$. 查询$x$数的排名(若有多个相同的数,因输出最小的排名)
    $4$. 查询排名为$x$的数
    $5$. 求$x$的前驱(前驱定义为小于$x$,且最大的数)
    $6$. 求$x$的后继(后继定义为大于$x$,且最小的数)


题目分析

平衡树模板题。

敲个替罪羊树。

果然比常数大的Splay跑得快。


代码

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#include<algorithm>
#include<iostream>
#include<iomanip>
#include<cstring>
#include<cstdlib>
#include<climits>
#include<vector>
#include<cstdio>
#include<cmath>
#include<queue>
using namespace std;

inline const int Get_Int() {
int num=0,bj=1;
char x=getchar();
while(x<'0'||x>'9') {
if(x=='-')bj=-1;
x=getchar();
}
while(x>='0'&&x<='9') {
num=num*10+x-'0';
x=getchar();
}
return num*bj;
}

const int maxn=100005;

struct Tree {
int child[2],father;
int size,val;
Tree() {}
Tree(int l,int r,int f,int s,int v):father(f),size(s),val(v) {
child[0]=l;
child[1]=r;
}
};

struct ScapeGoat_Tree {
const double alpha=0.7;
Tree tree[maxn];
int root,size;
#define ls(x) tree[x].child[0]
#define rs(x) tree[x].child[1]
#define fa(x) tree[x].father
#define val(x) tree[x].val
#define size(x) tree[x].size
ScapeGoat_Tree() {
tree[++size]=Tree(0,2,0,2,-INT_MAX);
tree[++size]=Tree(0,0,1,1,INT_MAX);
root=1;
}
bool balance(int index) {
return size(index)*alpha>=max(size(ls(index)),size(rs(index)));
}
bool checkson(int index) {
return rs(fa(index))==index;
}
void push_up(int index) {
size(index)=size(ls(index))+1+size(rs(index));
}
int cnt,a[maxn];
void dfs(int index) {
if(ls(index))dfs(ls(index));
a[++cnt]=index;
if(rs(index))dfs(rs(index));
}
int build(int Left,int Right) {
if(Left>Right)return 0;
int mid=(Left+Right)>>1,pos=a[mid];
ls(pos)=build(Left,mid-1);
rs(pos)=build(mid+1,Right);
fa(ls(pos))=fa(rs(pos))=pos;
push_up(pos);
return pos;
}
void rebuild(int index) {
cnt=0;
dfs(index);
int father=fa(index),side=checkson(index);
int pos=build(1,cnt);
tree[father].child[side]=pos;
fa(pos)=father;
if(index==root)root=pos;
}
void insert(int v) {
int now=root,father=0;
while(now) {
father=now;
size(father)++;
now=tree[now].child[val(now)<=v];
}
tree[now=++size]=Tree(0,0,father,1,v);
if(father)tree[father].child[val(father)<=v]=now;
int pos=0;
for(int i=now; i; i=fa(i))
if(!balance(i))pos=i;
if(pos)rebuild(pos);
}
void remove(int index) {
if(ls(index)&&rs(index)) {
int pre=ls(index);
while(rs(pre))pre=rs(pre);
val(index)=val(pre); //前驱复制
index=pre; //删除前驱
}
int son=ls(index)?ls(index):rs(index),side=checkson(index);
tree[fa(index)].child[side]=son;
fa(son)=fa(index);
for(int i=fa(index); i; i=fa(i))size(i)--;
if(index==root)root=son;
}
int find(int v) {
int now=root;
while(now) {
if(val(now)==v)return now;
else now=tree[now].child[val(now)<v];
}
return -1;
}
int rank(int v) {
int now=root,ans=0;
while(now) {
if(v<=val(now))now=ls(now);
else {
ans+=size(ls(now))+1;
now=rs(now);
}
}
return ans;
}
int kth(int rank) {
rank++;
int now=root;
while(now>0&&rank>=0) {
if(ls(now)&&size(ls(now))>=rank)now=ls(now);
else {
if(rank<=size(ls(now))+1)return now;
rank-=size(ls(now))+1;
now=rs(now);
}
}
return -1;
}
int pre(int num) {
int now=root,ans=-INT_MAX;
while(now) {
if(val(now)<num)ans=max(ans,val(now)),now=rs(now);
else now=ls(now);
}
return ans;
}
int suc(int num) {
int now=root,ans=INT_MAX;
while(now) {
if(val(now)>num)ans=min(ans,val(now)),now=ls(now);
else now=rs(now);
}
return ans;
}
} sgt;

int n;

int main() {
n=Get_Int();
for(int i=1; i<=n; i++) {
int order=Get_Int();
if(order==1)sgt.insert(Get_Int());
if(order==2)sgt.remove(sgt.find(Get_Int()));
if(order==3)printf("%d\n",sgt.rank(Get_Int()));
if(order==4)printf("%d\n",sgt.tree[sgt.kth(Get_Int())].val);
if(order==5)printf("%d\n",sgt.pre(Get_Int()));
if(order==6)printf("%d\n",sgt.suc(Get_Int()));
}
return 0;
}
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