SPOJ QTREE 树链剖分 边上剖分

题目链接：

#include <cstdio>
#include <cstring>
#include <algorithm>
#define sf scanf
#define pf printf
using namespace std;

/** Edge */
const int maxn = 10000 + 50;
int n;
struct Edge{
    int v,c,pre;
}Es[maxn * 2];
int head[maxn],TOT_EDGE;
void EDGE_INIT(){
    memset(head,-1,sizeof head);TOT_EDGE = 0;
}
inline void Add_Edge(int u,int v,int c){
    Es[TOT_EDGE].v = v;
    Es[TOT_EDGE].c = c;
    Es[TOT_EDGE].pre = head[u];
    head[u] = TOT_EDGE++;
}

/** TreeSplit */
int son[maxn],size[maxn],fa[maxn],dep[maxn];
int top[maxn],tid[maxn],rank[maxn],tot;
int DFS(int rt){
    dep[rt] = dep[fa[rt]] + 1;
    son[rt] = 0;
    size[rt] = 1;
    for(int i = head[rt];~i;i = Es[i].pre){
        int v = Es[i].v;
        if(v != fa[rt]){
            fa[v] = rt;
            size[rt] += DFS(v);
            if(size[son[rt]] < size[v]) son[rt] = v;
        }
    }
    return size[rt];
}

void Split(int rt,int tp){
    top[rt] = tp;
    tid[rt] = tot++;
    rank[tid[rt]] = rt;
    if(son[rt]){
        Split(son[rt],tp);
        for(int i = head[rt];~i;i = Es[i].pre){
            int v = Es[i].v;
            if(v != fa[rt] && v != son[rt]) Split(v,v);
        }
    }
}

inline void TreeLineSplit(){
    size[0] = 0;
    fa[1] = 1;
    dep[0] = 0;
    DFS(1);
    tot = 0;
    Split(1,1);
}


/** SegTree */
#define lson rt << 1 , l , mid
#define rson rt << 1 | 1,mid + 1,r
int MAX[maxn << 2],num[maxn];
void PushUp(int rt){
    MAX[rt] = max(MAX[rt << 1],MAX[rt << 1 | 1]);
}

void Build(int rt,int l,int r){
    if(l == r){
        MAX[rt] = num[l];
        return;
    }
    int mid = l + r >> 1;
    Build(lson);Build(rson);
    PushUp(rt);
}

void Update(int rt,int l,int r,int x,int c){
    if(l == r){
        MAX[rt] = c;
        return;
    }
    int mid = l + r >> 1;
    if(x <= mid) Update(lson,x,c);
    else Update(rson,x,c);
    PushUp(rt);
}

int Query(int rt,int l,int r,int L,int R){
    if(L <= l && R >= r) return MAX[rt];
    int mid = l + r >> 1;
    int ret = 0;
    if(L <= mid) ret = max(ret,Query(lson,L,R));
    if(R > mid) ret = max(ret,Query(rson,L,R));
    return ret;
}

inline void GetNumAr(){
    for(int i = 0;i < TOT_EDGE;i += 2){
        int u = Es[i].v,v = Es[i + 1].v,c = Es[i].c;
        if(dep[v] < dep[u]) swap(u,v);
        num[tid[v]] = c;
    }
}

/** ANS */
inline void CHANGE(int x,int c){
    int u = Es[(x - 1) * 2].v,v = Es[(x - 1) * 2 + 1].v;
    if(dep[v] < dep[u]) swap(u,v);
    Update(1,1,n - 1,tid[v],c);
}
inline int Ans_Query(int u,int v){
    int ret = 0;
    while(top[u] != top[v]){
        if(dep[top[v]] < dep[top[u]]) swap(u,v);
        ret = max(ret,Query(1,1,n - 1,tid[top[v]],tid[v]));
        v = fa[top[v]];
    }
    if(u == v) return ret;
    if(dep[v] < dep[u]) swap(u,v);
    return max(ret,Query(1,1,n - 1,tid[u] + 1,tid[v]));
}


char op[10];
int main(){
//    freopen("in.txt","r",stdin);
    int T;sf("%d",&T);
    while( T-- ){
        sf("%d",&n);
        EDGE_INIT();
        for(int i = 1;i < n;++i){
            int u,v,c;sf("%d%d%d",&u,&v,&c);
            Add_Edge(u,v,c);
            Add_Edge(v,u,c);
        }
        TreeLineSplit();
        GetNumAr();
        Build(1,1,n - 1);
        int x,y;
        while( sf("%s",op) ){
            if(op[0] == 'D') break;
            sf("%d%d",&x,&y);
            if(op[0] == 'Q') pf("%d\n",Ans_Query(x,y));
            else CHANGE(x,y);
        }
    }
    return 0;
}