HDU 5692 (DFS序+线段树)

DFS获得从0到每一个顶点的距离，同时获得L和R数组。两数组为遍历时从i进入再从i出来的序列。

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
using namespace std;
const int maxn = 1e5+5;

typedef long long ll;
const ll inf = 0x3f3f3f3f3f3f3f3f;
int n,m;
vector<int> g[maxn];
ll w[maxn];
int index = 1;
int L[maxn],R[maxn];
int vis[maxn];
ll d[maxn];
struct node
{
    ll maxx;
    ll lazy;
};
node T[maxn*5];
void dfs(int x,int New)
{
    L[x] = index;
    for(int i=0;i<g[x].size();i++)
    {
        int v = g[x][i];
        if(!vis[v])
        {
            vis[v] = 1;
           index++;
           d[index] = d[New]+w[v];
           dfs(v,index);
        }
    }
    R[x] = index;
}
void build(int q,int l,int r)
{
    if(l==r)
    {
        T[q].maxx = d[l];
        T[q].lazy = 0;
        return;
    }
    int mid = (l+r)/2;
    build(q*2,l,mid);
    build(q*2+1,mid+1,r);
    T[q].lazy = 0;
    T[q].maxx = max(T[q*2].maxx,T[q*2+1].maxx);
}
void ins(int q,int l,int r,int ql,int qr,ll tt)
{
    if(ql<=l&&r<=qr)
    {
        T[q].maxx += tt;
        T[q].lazy += tt;
        return;
    }
    if(T[q].lazy)
    {
        T[q*2].maxx += T[q].lazy;
        T[q*2].lazy += T[q].lazy;
        T[q*2+1].maxx += T[q].lazy;
        T[q*2+1].lazy += T[q].lazy;
        T[q].lazy = 0;
    }
    int mid = (l+r)/2;
    if(ql<=mid) ins(q*2,l,mid,ql,qr,tt);
    if(mid+1<=qr) ins(q*2+1,mid+1,r,ql,qr,tt);
    T[q].maxx = max(T[q*2].maxx,T[q*2+1].maxx);
    return;
}
ll query(int q,int l,int r,int ql,int qr)
{
    if(ql<=l&&qr>=r)
    {
        return T[q].maxx;
    }
    if(T[q].lazy)
    {
        T[q*2].maxx += T[q].lazy;
        T[q*2].lazy += T[q].lazy;
        T[q*2+1].maxx += T[q].lazy;
        T[q*2+1].lazy += T[q].lazy;
        T[q].lazy = 0;
    }
    ll maxx = -inf;   //坑点
    int mid = (l+r)/2;
    if(ql<=mid) maxx = max(maxx,query(q*2,l,mid,ql,qr));
    if(mid+1<=qr) maxx = max(maxx,query(q*2+1,mid+1,r,ql,qr));
    return maxx;
}
int main()
{
    int T,kase = 0;cin>>T;
    while(T--)
    {
        scanf("%d %d",&n,&m);
        for(int i=0;i<=n;i++) g[i].clear();
        int xx,xy;
        for(int i=1;i<=n-1;i++)
        {
            scanf("%d %d",&xx,&xy);
            g[xx].push_back(xy);
            g[xy].push_back(xx);
        }
        for(int i=0;i<n;i++) scanf("%I64d",&w[i]);
        index = 1;
        memset(d,0,sizeof(d));
        memset(vis,0,sizeof(vis));
        memset(L,0,sizeof(L));
        memset(R,0,sizeof(R));
        d[1] = w[0];
        vis[0] = 1;
        dfs(0,1);
        build(1,1,n);
        printf("Case #%d:
",++kase);
        int x,y;
        ll ttt;
        for(int i=1;i<=m;i++)
        {
            scanf("%d %d",&x,&y);
            if(x==1)
            {
                printf("%I64d
",query(1,1,n,L[y],R[y]));
            }
            else
            {
                scanf("%I64d",&ttt);
                ll tt = ttt-w[y];
                ins(1,1,n,L[y],R[y],tt);
                w[y] = ttt;  //坑点
            }
        }
    }
    return 0;
}