树链剖分 poj 2763

#include<stdio.h>
#include<string.h>
#include<algorithm>

using namespace std;

#define MAXN  100010
struct edge
{
    int from,to,w,next;
}x[MAXN<<1],s1[MAXN];

int head[MAXN],siz[MAXN],father[MAXN],dep[MAXN],top[MAXN],intree[MAXN],outtree[MAXN],son[MAXN],val[MAXN];
int cnt,tim,n;

void add(int u,int v,int w)
{
    x[cnt].from=u;
    x[cnt].to=v;
    x[cnt].w=w;
    x[cnt].next=head[u];
    head[u]=cnt++;
}

void dfs1(int u,int fa)
{
    siz[u]=1;
    father[u]=fa;
    dep[u]=dep[fa]+1;
    for(int i=head[u];i!=-1;i=x[i].next)
    {
        int v=x[i].to;
        if(v==fa)
            continue;
        dfs1(v,u);
        siz[u]+=siz[v];
        if(siz[v]>siz[son[u]])
            son[u]=v;
    }
}

void dfs2(int u,int tp)
{
    top[u]=tp;
    intree[u]=++tim;
    outtree[tim]=u;
    if(son[u]!=0)
        dfs2(son[u],tp);
    for(int i=head[u];i!=-1;i=x[i].next)
    {
        int v=x[i].to;
        if(v==son[u]||v==father[u])
            continue;
        dfs2(v,v);
    }

}
struct node
{
    int l,r,w;
}z[MAXN<<3];

void Build(int l,int r,int a)
{
    z[a].l=l;
    z[a].r=r;
    if(l==r)
    {
        z[a].w=val[l];
        return ;
    }
    int mid=(l+r)>>1;
    Build(l,mid,a<<1);
    Build(mid+1,r,a<<1|1);
    z[a].w=z[a<<1].w+z[a<<1|1].w;
}
void update(int l,int r,int a1,int w,int a)//单点更新
{
    if(l==r)
    {
        z[a].w=w;
        return ;
    }
    int mid=(l+r)>>1;
    if(a1<=mid)
        update(l,mid,a1,w,a<<1);
    else
        update(mid+1,r,a1,w,a<<1|1);
    z[a].w=z[a<<1].w+z[a<<1|1].w;
}
int ques(int l,int r,int a1,int b1,int a)//区间求和
{
    int ans=0;
    if(a1<=l&&r<=b1)
        return z[a].w;
    int mid=(l+r)>>1;
    if(a1<=mid)
        ans+=ques(l,mid,a1,b1,a<<1);
    if(b1>mid)
        ans+=ques(mid+1,r,a1,b1,a<<1|1);
    return ans;
}
int change(int x,int y)
{
    int ans=0;

    while(top[x] != top[y])
    {
        if(dep[top[x]]<dep[top[y]])
            swap(x,y);
        ans+=ques(1,n,intree[top[x]],intree[x],1);
        x=father[top[x]];
    }

    if(x==y)
        return ans;
    if(dep[x] > dep[y])
        swap(x,y);

    ans+=ques(1,n,intree[x]+1,intree[y],1);//这边左边的是要加1的
    return ans;
}

int main()
{
    int q,s;
    while(scanf("%d%d%d",&n,&q,&s)!=EOF)  
    {
        memset(head,-1,sizeof(head));
        memset(son,0,sizeof(son));
        cnt=1;
        tim=0;
        for(int i=1;i<n;i++)
        {
            int u,v,w;
            scanf("%d%d%d",&s1[i].from,&s1[i].to,&s1[i].w);//存到另外一个数组里
            add(s1[i].from,s1[i].to,s1[i].w);
            add(s1[i].to,s1[i].from,s1[i].w);
        }
        dfs1(1,0);
        dfs2(1,1);
        for(int i=1;i<n;i++) //边的权放到点上 那么只要区间求和就可以了 其实里面还有问题
        {
            if(dep[s1[i].from]<dep[s1[i].to])
                swap(s1[i].from,s1[i].to);
            val[intree[s1[i].from]]=s1[i].w;
        }
        Build(1,n,1);
        while(q--)
        {
            int a;
            scanf("%d",&a);
            if(a==0)
            {
                int b;
                scanf("%d",&b);
                printf("%d\n",change(s,b));
                s=b;
            }
            else
            {
                int b,c;
                scanf("%d%d",&b,&c);
                update(1,n,intree[s1[b].from],c,1);
            }
        }
    }

    return 0;
}