bzoj 1180: [CROATIAN2009]OTOCI

#include<cstdio>
#include<iostream>
const int maxn =60007;
int n,m;
int top=0;
int ch[maxn][2],fa[maxn],stack[maxn];
int ans[maxn],v[maxn];
bool rev[maxn];
inline int read() {
    int x=0;
    char c=getchar();
    while(c<‘0‘||c>‘9‘) c=getchar();
    while(c<=‘9‘&&c>=‘0‘) x=x*10+c-‘0‘,c=getchar();
    return x;
}
void update(int x) {
    ans[x]=ans[ch[x][1]]+ans[ch[x][0]]+v[x];    
}
bool isroot(int x) {
    return ch[fa[x]][1]!=x&&ch[fa[x]][0]!=x;
}
void pushdown(int x) {
    if(rev[x]) {
        rev[x]^=1;
        rev[ch[x][0]]^=1;rev[ch[x][1]]^=1;std::swap(ch[x][1],ch[x][0]);
    }
}
void rotate(int x) {
    int y=fa[x],z=fa[y],d=(ch[y][1]==x)^1;
    if(!isroot(y)) ch[z][ch[z][1]==y]=x;
    fa[x]=z;
    ch[y][d^1]=ch[x][d],fa[ch[x][d]]=y;
    ch[x][d]=y;fa[y]=x;
    update(y);update(x);
}
void splay(int x) {
    stack[++top]=x;
    for(int i=x;!isroot(i);i=fa[i]) stack[++top]=fa[i];
    while(top)pushdown(stack[top--]);
    while(!isroot(x)) {
        int y=fa[x],z=fa[y];
        if(!isroot(y)) {
            if(ch[y][1]==x^ch[z][1]==y)rotate(x);
            else rotate(y);
        }
        rotate(x);
    }
    return ;
}
void access(int x) {
    for(int i=0;x;i=x,x=fa[x]) { 
        splay(x);
        ch[x][1]=i;update(x);
    }
}
void makeroot(int x) {
    access(x),splay(x);rev[x]^=1;
}
void link(int x,int y) {
    makeroot(x),fa[x]=y;return splay(x);
}
int find(int x) {
    for(access(x),splay(x);ch[x][0];x=ch[x][0]) ;
    return x;
}
void split(int x,int y) {
    makeroot(x),access(y);
    return splay(y);
}
int query(int x,int y) {
    split(x,y);return ans[y];
}
void modify(int x,int y) {
    access(x),splay(x),v[x]=y;
    return update(x);
}
int main() {
    n=read();
    for(int i=1;i<=n;++i) {
        v[i]=read();ans[i]=v[i];
    }
    m=read();
    char c[70];
    for(int a,b;m;m--) {
        scanf("%s",c),a=read(),b=read();
        if(c[0]==‘b‘) {
            if(find(a)==find(b))puts("no");
            else puts("yes"),link(a,b);
        }
        else if(c[0]==‘p‘) {
            modify(a,b);    
        }
        else {
            if(find(a)!=find(b))puts("impossible");
            else printf("%d\n",query(a,b));    
        }
    }
    return 0;
}