2002: [Hnoi2010]Bounce 弹飞绵羊

2002: [Hnoi2010]Bounce 弹飞绵羊

https://www.lydsy.com/JudgeOnline/problem.php?id=2002

分析：

　　绵羊在弹飞的路径中相当于一棵树，这棵树需要更改形态，删一条边，加一条边，所以LCT维护一下。

代码：

 #include<bits/stdc++.h>
 using namespace std;
 typedef long long LL;

 inline int read() {
     int x=,f=;char ch=getchar();for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-;
     for (;isdigit(ch);ch=getchar())x=x*+ch-'';return x*f;
 }

 const int N = ;
 int ch[N][],fa[N],rev[N],val[N],siz[N],sk[N],a[N],Top,n;

 void pushup(int x) {
     siz[x] = siz[ch[x][]] + siz[ch[x][]] + ;
 }
 void pushdown(int x) {
     if (rev[x]) {
         rev[ch[x][]] ^= ; rev[ch[x][]] ^= ;
         swap(ch[x][], ch[x][]);
         rev[x] ^= ;
     }
 }
 bool isroot(int x) {
     return ch[fa[x]][] != x && ch[fa[x]][] != x;
 }
 int son(int x) {
     return x == ch[fa[x]][];
 }
 void rotate(int x) {
     int y = fa[x],z = fa[y],b = son(x),c = son(y),a = ch[x][!b];
     if (!isroot(y)) ch[z][c] = x;fa[x] = z;
     ch[x][!b] = y;fa[y] = x;
     ch[y][b] = a;if (a) fa[a] = y;
     pushup(y);pushup(x);
 }
 void splay(int x) {
     sk[Top = ] = x;
     for (int i=x; !isroot(i); i=fa[i]) sk[++Top] = fa[i];
     while (Top) pushdown(sk[Top--]);
     while (!isroot(x)) {
         int y = fa[x];
         if (isroot(y)) rotate(x);
         else {
             if (son(x) == son(y)) rotate(y), rotate(x);
             else rotate(x), rotate(x);
         }
     }
 }
 void access(int x) {
     for (int last=; x; last=x, x=fa[x]) {
         splay(x); ch[x][] = last; pushup(x);
     }
 }
 void makeroot(int x) {
     access(x); splay(x); rev[x] ^= ;
 }
 int find(int x) {
     access(x); splay(x);
     while (ch[x][]) x = ch[x][];
     return x;
 }
 void link(int x,int y) {
     makeroot(x);
     fa[x] = y;
 }
 void cut(int x,int y) {
     makeroot(x); access(y); splay(y);
     if (fa[x] == y && !ch[x][]) fa[x] = ch[y][] = ;
 }

 void query() {
     makeroot(n + );
     int p = read() + ;
     access(p);
     splay(p);
     printf("%d\n",siz[p] - );
 }
 void change() {
     int p = read() + ,x = read(),t = p+x > n+ ? n+: p+x; // --- 判断是否大于n+1，不判luogu上80
     cut(p,a[p]);
     a[p] = t;
     link(p,a[p]);
 }

 int main() {
     n = read();
     for (int i=; i<=n; ++i) {
         a[i] = i + read();
         a[i] = a[i] > n+ ? n+ : a[i];
     }
     for (int i=; i<=n; ++i) link(i,a[i]);
     int m = read();
     while (m--) {
         int opt = read();
         if (opt == ) query();
         else change();
     }
     return ;
 }