SPOJ QTREE - Query on a tree

#include<cstdio>
#include<cstring>
#include<algorithm>
#define MN 10010
using namespace std;

int p,ca,f;
inline int read(){
    p=0;ca=getchar();f=1;
    while(ca<‘0‘||ca>‘9‘) {if (ca==‘-‘) f=-1;ca=getchar();}
    while(ca>=‘0‘&&ca<=‘9‘) p=p*10+ca-48,ca=getchar();
    return p*f;
}
struct na{
    int y,ne,c,nu;
}b[MN*2];
int fa[MN],n,t,x,y,c,l[MN],r[MN],num,id[MN],key[MN],ch[MN][2],ma[MN];
bool rt[MN];
inline int max(int a,int b){return a>b?a:b;}
inline void update(int x){
    ma[x]=max(max(ma[ch[x][0]],ma[ch[x][1]]),key[x]);
}
inline void rot(int x){
    int y=fa[x],kind=ch[y][1]==x;
    fa[x]=fa[y];
    fa[y]=x;
    ch[y][kind]=ch[x][!kind];
    fa[ch[y][kind]]=y;
    ch[x][!kind]=y;
    if(rt[y]) rt[y]=0,rt[x]=1;else ch[fa[x]][ch[fa[x]][1]==y]=x;
    update(y);update(x);
}
inline void splay(int x){
    while(!rt[x]){
        if (rt[fa[x]]) rot(x);else
        if ((ch[fa[fa[x]]][1]==fa[x])==(ch[fa[x]][1]==x)) rot(fa[x]),rot(x);else rot(x),rot(x);
    }
}
inline void acc(int u){
    int x=0;
    while(u){
        splay(u);
        rt[ch[u][1]]=1;rt[ch[u][1]=x]=0;
        update(u);
        u=fa[x=u];
    }
}
inline void change(int x,int c){
    acc(x);
    key[x]=c;
    update(x);
}
inline void lca(int &u,int &v){
    acc(v);v=0;
    while(u){
        splay(u);
        if (!fa[u]) break;
        rt[ch[u][1]]=1;
        rt[ch[u][1]=v]=0;
        update(u);
        u=fa[v=u];
    }
}
inline int qu(int x,int y){
    lca(x,y);
    return max(ma[y],ma[ch[x][1]]);
}
inline void in(int x,int y,int c,int nu){
    num++;
    if (!l[x]) l[x]=num;else b[r[x]].ne=num;
    b[num].y=y;b[num].c=c;b[num].ne=0;b[num].nu=nu;r[x]=num;
}
inline void dfs(int x){
    for (int i=l[x];i;i=b[i].ne)
    if (!fa[b[i].y]){
        fa[b[i].y]=x;
        id[b[i].nu]=b[i].y;
        key[b[i].y]=b[i].c;
        dfs(b[i].y);
    }
}
char ss[10];
int main(){
    t=read();
    ma[0]=-1e9;
    while(t--){
        num=0;
        memset(rt,1,sizeof(rt));
        memset(fa,0,sizeof(fa));
        memset(ch,0,sizeof(ch));
        memset(l,0,sizeof(l));
        n=read();
        for (int i=1;i<n;i++){
            x=read();y=read();c=read();
            in(x,y,c,i);
            in(y,x,c,i);
        }
        fa[1]=-1;
        dfs(1);
        fa[1]=0;
        for(;;){
            scanf("%s",ss);
            if (ss[0]==‘D‘) break;
            x=read();y=read();
            if (ss[0]==‘Q‘) printf("%d\n",qu(x,y));else
            change(id[x],y);
        }
    }
}