FZU 2082 过路费

树链剖分模板题

#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
#define N 50010
#define ls o<<1
#define rs o<<1|1
#define define_m int m=(l+r)>>1
#define ll long long
int first[N] , k;
struct Edge{
    int x , y , next , w;
}e[N<<1];

void add_edge(int x , int y , int w)
{
    e[k].x = x , e[k].y = y , e[k].next = first[x] , e[k].w = w;
    first[x] = k++;
}

int sz[N] , dep[N] , fa[N] , son[N] , top[N] , id[N] , num;
void dfs(int u , int f , int d)
{
    fa[u] = f , sz[u] = 1 , dep[u]= d , son[u]=0;
    int mx = 0;
    for(int i=first[u] ; ~i ; i=e[i].next){
        int v = e[i].y;
        if(v == f) continue;
        dfs(v , u , d+1);
        sz[u]+=sz[v];
        if(sz[v]>mx) mx=sz[v] , son[u]=v;
    }
}

void dfs1(int u , int f , int head)
{
    top[u]=head , id[u]=++num;
    if(son[u]) dfs1(son[u] , u , head);
    for(int i=first[u] ; ~i ; i=e[i].next){
        int v = e[i].y;
        if(v == f || v == son[u]) continue;
        dfs1(v , u , v);
    }
}

ll sum[N<<2] ;
int val[N];
void push_up(int o)
{
    sum[o] = sum[ls]+sum[rs];
}

void build(int o , int l , int r)
{
    if(l==r){
        sum[o]=(ll)val[l];
        return ;
    }
    define_m;
    build(ls , l , m);
    build(rs , m+1 , r);
    push_up(o);
}

void update(int o , int l , int r , int p , int v)
{
    if(l==r){
        sum[o]=(ll)v;
        return;
    }
    define_m;
    if(m>=p) update(ls , l , m , p , v);
    else update(rs , m+1 , r , p , v);
    push_up(o);
}

ll qSum(int o , int l , int r , int s , int t)
{
    if(l>=s && r<=t) return sum[o];
    define_m;
    ll res = 0;
    if(m>=s) res+=qSum(ls , l , m , s , t);
    if(m<t) res+=qSum(rs , m+1 , r , s , t);
    return res;
}

ll calPath(int u , int v)
{
    int top1 = top[u] , top2 = top[v] ;
    ll ret=0;
    while(top1!=top2){
        if(dep[top1]<dep[top2]){
            swap(top1 , top2);
            swap(u , v);
        }
        ret+=qSum(1 , 1 , num , id[top1] , id[u]);
        u = fa[top1];
        top1 = top[u];
    }
    if(u!=v){
        if(dep[u]<dep[v]) swap(u,v);
        ret+=qSum(1,1,num,id[son[v]],id[u]);
    }
    return ret;
}

int main()
{
  //  freopen("in.txt" , "r" , stdin);
    int n , m , x , y , w;
    while(scanf("%d%d" , &n , &m)!=EOF)
    {
        memset(first , -1 , sizeof(first));
        k = 0;
        for(int i=0 ; i<n-1 ; i++){
            scanf("%d%d%d" , &x , &y , &w);
            add_edge(x , y , w);
            add_edge(y , x , w);
        }
        dfs(1 , 0 , 1);
        num = 0;
        dfs1(1 , 0 , 1);
        for(int i=0 ; i<n-1 ; i++){
            x = e[i*2].x , y = e[i*2].y;
            if(fa[x]!=y) val[id[y]] = e[i*2].w;
            else val[id[x]] = e[i*2].w;
        }
        build(1 , 1 , num);
        while(m--){
            scanf("%d%d%d" , &w , &x , &y);
            if(w){
                printf("%I64d
" , calPath(x , y));
            }else{
                x--;
                int pos;
                if(fa[e[x*2].x]!=e[x*2].y) pos = id[e[x*2].y];
                else pos = id[e[x*2].x];
                update(1 , 1 , num , pos , y);
            }
        }
    }
    return 0;
}