fzu2082 过路费 树链剖分

题意：中文题。。

思路：树链剖分后，在线段树上单点更新，区间查询。详见代码：

/*********************************************************  file name: fzu2082.cpp  author : kereo  create time:  2015年01月21日 星期三 09时21分42秒*********************************************************/#include<iostream>#include<cstdio>#include<cstring>#include<queue>#include<set>#include<map>#include<vector>#include<stack>#include<cmath>#include<string>#include<algorithm>using namespace std;typedef long long ll;const int sigma_size=26;const int N=100+50;const int MAXN=50000+50;const int inf=0x3fffffff;const double eps=1e-8;const int mod=100000000+7;#define L(x) (x<<1)#define R(x) (x<<1|1)#define PII pair<int, int>#define mk(x,y) make_pair((x),(y))int n,m,edge_cnt,cnt;int head[MAXN],sz[MAXN],son[MAXN],fa[MAXN],top[MAXN],dep[MAXN],pos[MAXN];struct Edge{    int u,v,w,next;}edge[MAXN<<1];struct node{    int l,r;    ll sum;}segtree[MAXN<<2];void init(){    edge_cnt=cnt=0;    memset(head,-1,sizeof(head));}void addedge(int u,int v,int w){    edge[edge_cnt].u=u; edge[edge_cnt].v=v;      edge[edge_cnt].w=w; edge[edge_cnt].next=head[u]; head[u]=edge_cnt++;}void dfs1(int u,int pre,int depth){    sz[u]=1; son[u]=0; dep[u]=depth; fa[u]=pre;    for(int i=head[u];i!=-1;i=edge[i].next){        int v=edge[i].v;        if(v == pre)            continue;        dfs1(v,u,depth+1);        sz[u]+=sz[v];        if(sz[son[u]]<sz[v])            son[u]=v;    }}void dfs2(int u,int tp){    pos[u]=cnt++; top[u]=tp;    if(son[u]!=0)        dfs2(son[u],top[u]);    for(int i=head[u];i!=-1;i=edge[i].next){        int v=edge[i].v;        if(v == fa[u] || v == son[u])            continue;        dfs2(v,v);    }}void build(int rt,int l,int r){    segtree[rt].l=l; segtree[rt].r=r; segtree[rt].sum=0;    if(l == r)        return ;    int mid=(l+r)>>1;    build(L(rt),l,mid); build(R(rt),mid+1,r);}void push_up(int rt){    segtree[rt].sum=segtree[L(rt)].sum+segtree[R(rt)].sum;}void update(int rt,int p,int x){    if(segtree[rt].l == segtree[rt].r){        segtree[rt].sum=x;        return ;    }    int mid=(segtree[rt].l+segtree[rt].r)>>1;    if(p<=mid)        update(L(rt),p,x);    else         update(R(rt),p,x);    push_up(rt);}ll query(int rt,int l,int r){    if(segtree[rt].l == l && segtree[rt].r == r)        return segtree[rt].sum;    int mid=(segtree[rt].l+segtree[rt].r)>>1;    if(r<=mid)        return query(L(rt),l,r);    else if(l>mid)        return query(R(rt),l,r);    else         return query(L(rt),l,mid)+query(R(rt),mid+1,r);}ll solve(int u,int v){    ll ans=0;    while(top[u]!=top[v]){        if(dep[top[u]]<dep[top[v]])            swap(u,v);        ans+=query(1,pos[top[u]],pos[u]);        u=fa[top[u]];    }    if(dep[u]>dep[v])        swap(u,v);    if(u!=v)        ans+=query(1,pos[u]+1,pos[v]);    return ans;}int main(){    while(~scanf("%d%d",&n,&m)){        init();        for(int i=1;i<n;i++){            int u,v,w;            scanf("%d%d%d",&u,&v,&w);            addedge(u,v,w); addedge(v,u,w);        }        dfs1(1,1,1); dfs2(1,1); build(1,1,n-1);        for(int i=0;i<edge_cnt;i+=2){            int u=edge[i].u,v=edge[i].v,w=edge[i].w;            if(dep[u]<dep[v])                swap(u,v);            update(1,pos[u],w);        }        for(int i=0;i<m;i++){            int id,u,v;            scanf("%d",&id);            if(id == 0){                int x,w;                scanf("%d%d",&x,&w);                x=(x-1)*2;                u=edge[x].u; v=edge[x].v;                if(dep[u]<dep[v])                    swap(u,v);                update(1,pos[u],w);            }            else{                scanf("%d%d",&u,&v);                printf("%lld\n",solve(u,v));            }        }    }return 0;}