[BZOJ]2733永无乡 做题笔记

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
using namespace std;
const int MAX=100009;
struct Splay {
int a[MAX],f[MAX],s[MAX],fa[MAX];
int ch[MAX][2];
int find (int x) {
if (x==fa[x]) return x;
fa[x]=find(fa[x]);
return fa[x];
}
void update (int x) {
s[x]=s[ch[x][0]]+s[ch[x][1]]+1;
}
void rotate(int x) {
int y=f[x],opt;
if (ch[f[x]][0]==x) opt=0;
else opt=1;
ch[y][opt]=ch[x][!opt];
if (ch[x][!opt]) f[ch[x][!opt]]=y;
f[x]=f[y];
if (f[y])
if (ch[f[y]][0]==y) ch[f[y]][0]=x;
else ch[f[y]][1]=x;
f[y]=x,ch[x][!opt]=y;
update(y),update(x);
}
void splay (int x,int to=0) {
while (f[x]!=to) {
if (f[f[x]]==to) rotate(x);
else if ((ch[f[f[x]]][0]==f[x])==
(ch[f[x]][0]==x))
rotate(f[x]),rotate(x);
else rotate(x),rotate(x);
}
}
void insert (int x,int y) {
while (1) {
if (a[y]<=a[x]) {
if (ch[x][0]) x=ch[x][0];
else {
f[y]=x;
ch[x][0]=y;
break;
}
}
else {
if (ch[x][1]) x=ch[x][1];
else {
f[y]=x;
ch[x][1]=y;
break;
}
}
}
update(x);
splay(y);
}
void merge (int x,int y) {
if (!y) return ;
merge(x,ch[y][0]);
merge(x,ch[y][1]);
ch[y][0]=ch[y][1]=0;s[y]=1;
insert(x,y);
}
void addedge (int x,int y) {
int fx=find(x);
int fy=find(y);
if (fx!=fy) {
fa[fy]=fx;
splay(x);splay(y);
if (s[x]<s[y]) swap(x,y);
merge(x,y);
}
}
int find_by_rank (int x,int k) {
while (x) {
if (s[ch[x][0]]+1==k) return x;
if (k<s[ch[x][0]]+1) x=ch[x][0];
else k-=s[ch[x][0]]+1,x=ch[x][1];
}
return 0;
}
void query (int x,int k) {
splay(x);
if (k>s[x]) { puts("-1");return ; }
printf("%d\n",find_by_rank(x,k));
}
}Sp;
int n,m,q;
int main () {
int a,b;
char ch;
scanf("%d%d",&n,&m);
for (int i=1;i<=n;i++) {
scanf("%d",&Sp.a[i]);
Sp.fa[i]=i;
Sp.s[i]=1;
}
for (int i=1;i<=m;i++) {
scanf("%d%d",&a,&b);
Sp.addedge(a,b);
}
scanf("%d",&q);
for (int i=1;i<=q;i++) {
while ((ch=getchar())!='Q'&&ch!='B');
if (ch=='Q') {
scanf("%d%d",&a,&b);
Sp.query(a,b);
}
else if (ch=='B') {
scanf("%d%d",&a,&b);
Sp.addedge(a,b);
}
}
return 0;
}