FZU - 2082 过路费（树链剖分）

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题意：题目已经描述的很清晰了嘛～

分析：数链剖分模板题

参考代码：

#include
#include
#include
#include
#include

using namespace std;
#define mem(a,b) memset(a,b,sizeof(a))
#define lson rt<<1
#define rson rt<<1|1
typedef long long ll;
const int maxn = 5e4+10;
int n,m;
int e[maxn][3];
int head[maxn],tot;
struct Edge{
    int to,next;
};
Edge edge[maxn];
int poi;
int fa[maxn],son[maxn],siz[maxn],dep[maxn];
int p[maxn],fp[maxn],top[maxn];
int a[maxn];
//线段树，单点更新，区间查询
int sum[maxn<<2];

void Init()
{
    tot = poi = 0;
    mem(head,-1);
    mem(son,-1);
}

void AddEdge( int u, int v)
{
    edge[tot].to = v;
    edge[tot].next = head[u];
    head[u] = tot++;
}

void dfs1( int u, int pre, int d)
{
    siz[u] = 1;
    fa[u] = pre;
    dep[u] = d;
    for( int i = head[u]; ~i; i = edge[i].next)
    {
        int v = edge[i].to;
        if( v != pre)
        {
            dfs1(v,u,d+1);
            siz[u] += siz[v];
            if( son[u] == -1 || siz[v] > siz[son[u]])
                son[u] = v;
        }
    }
}

void dfs2( int u, int tp)
{
    p[u] = ++poi;
    fp[p[u]] = u;
    top[u] = tp;
    if( son[u] == -1)
        return;
    dfs2(son[u],tp);
    for( int i = head[u]; ~i; i = edge[i].next)
    {
         int v = edge[i].to;
         if( v != fa[u] && v != son[u])
            dfs2(v,v);
    }
}

void PushUp( int rt)
{
    sum[rt] = sum[lson]+sum[rson];
}

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

void Update( int l, int r, int rt, int pos, int val)
{
    if( l == pos && r == pos)
    {
        sum[rt] = val;
        return;
    }
    int mid = (l+r)>>1;
    if( pos <= mid)
        Update(l,mid,lson,pos,val);
    else
        Update(mid+1,r,rson,pos,val);
    PushUp(rt);
}

ll Query( int l, int r, int rt, int L, int R)
{
    if( l == L && r == R)
        return sum[rt];
    int mid = (l+r)>>1;
    if( R <= mid)
        return Query(l,mid,lson,L,R);
    else if( L > mid)
        return Query(mid+1,r,rson,L,R);
    else
        return Query(l,mid,lson,L,mid)+Query(mid+1,r,rson,mid+1,R);
}

ll Find( int u, int v)
{
    ll ans = 0;
    int t1 = top[u];
    int t2 = top[v];
    while( t1 != t2)
    {
        if( dep[t1] < dep[t2])
        {
            swap(u,v);
            swap(t1,t2);
        }
        ans += Query(1,poi,1,p[t1],p[u]);
        u = fa[t1];
        t1 = top[u];
    }
    if( u == v)
        return ans;
    if( dep[u] > dep[v])
        swap(u,v);
    return ans+Query(1,poi,1,p[son[u]],p[v]);
}

int main()
{
    while( ~scanf("%d%d",&n,&m))
    {
        Init();
        for( int i = 1; i < n; i++)
        {
            scanf("%d%d%d",&e[i][0],&e[i][1],&e[i][2]);
            AddEdge(e[i][0],e[i][1]);
            AddEdge(e[i][1],e[i][0]);
        }
        dfs1(1,0,0);
        dfs2(1,1);
        Build(1,poi,1);
        for( int i = 1; i < n; i++)
        {
            if( dep[e[i][0]] > dep[e[i][1]])
                swap(e[i][0],e[i][1]);
            Update(1,poi,1,p[e[i][1]],e[i][2]);
            a[p[e[i][1]]] = e[i][2];
        }
//        Build(1,poi,1);

        while( m--)
        {
            int op,a,b;
            scanf("%d%d%d",&op,&a,&b);
            if( op == 0)
                Update(1,poi,1,p[e[a][1]],b);
            else if( op == 1)
                printf("%lld\n",Find(a,b));
        }
    }

    return 0;
}