hdu5692 dfs序线段树

Posted 2020-10-15 walfy

这是补的知识点，按先序遍历的顺序建立dfs序，用左右两个值代表整个区间，因为dfs序最重要的特点就是子树的区间是连续的

建立线段树时，需要用重新标过的 下标来建立

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<map>
#include<set>
#include<list>
#include<cmath>
#include<queue>
#include<stack>
#include<vector>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define pil pair<int,ll>
#define C 0.5772156649
#define pi acos(-1.0)
#define ll long long
#define mod 1000000007
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1

using namespace std;

const double g=10.0,eps=1e-12;
const int N=100000+10,maxn=90000+10,inf=0x3f3f3f3f;

struct edge{
    int to,Next;
}e[N*2];
int cnt,head[N];
void add(int u,int v)
{
    e[cnt].to=v;
    e[cnt].Next=head[u];
    head[u]=cnt++;
}
int l[N],r[N],id[N],num;
ll a[N],d[N];
void dfs(int u,int f)
{
    num++;
    l[u]=num;
    id[num]=u;
    for(int i=head[u]; ~i; i=e[i].Next)
    {
        int x=e[i].to;
        if(x==f)continue;
        d[x]=d[u]+a[x];
        dfs(x,u);
    }
    r[u]=num;
}
ll lazy[N*4],sum[N*4];
void pushup(int rt)
{
    sum[rt]=max(sum[rt<<1],sum[rt<<1|1]);
}
void pushdown(int rt)
{
    if(lazy[rt])
    {
        lazy[rt<<1]+=lazy[rt];
        lazy[rt<<1|1]+=lazy[rt];
        sum[rt<<1]+=lazy[rt];
        sum[rt<<1|1]+=lazy[rt];
        lazy[rt]=0;
    }
}
void build(int l,int r,int rt)
{
    lazy[rt]=0;
    if(l==r)
    {
        sum[rt]=d[id[l]];
        return ;
    }
    int m=(l+r)>>1;
    build(ls);
    build(rs);
    pushup(rt);
}
void update(int L,int R,int v,int l,int r,int rt)
{
    if(L<=l&&r<=R)
    {
        sum[rt]+=v;
        lazy[rt]+=v;
        return ;
    }
    //if(l==r)return ;
    pushdown(rt);
    int m=(l+r)>>1;
    if(L<=m)update(L,R,v,ls);
    if(R>m)update(L,R,v,rs);
    pushup(rt);
}
ll query(int L,int R,int l,int r,int rt)
{
    if(L<=l&&r<=R)return sum[rt];
    //cout<<L<<" "<<l<<" "<<r<<" "<<R<<endl;
    // if(l==r)return -1e18;
    pushdown(rt);
    int m=(l+r)>>1;
    ll ans=-1e18;
    if(L<=m)ans=max(ans,query(L,R,ls));
    if(R>m)ans=max(ans,query(L,R,rs));
    return ans;
}
int main()
{
    /*  ios::sync_with_stdio(false);
      cin.tie(0);*/
    int t,res=0;
    scanf("%d",&t);
    while(t--)
    {
        printf("Case #%d:\n",++res);
        int n,m;
        scanf("%d%d",&n,&m);
        cnt=0;
        memset(head,-1,sizeof head);
        for(int i=1; i<n; i++)
        {
            int x,y;
            scanf("%d%d",&x,&y);
            add(x,y);
            add(y,x);
        }
        for(int i=0; i<n; i++)scanf("%I64d",&a[i]);
        d[0]=a[0],num=0;
        dfs(0,-1);
        build(1,n,1);
        while(m--)
        {
            int op;
            scanf("%d",&op);
            if(op==0)
            {
                int x,y;
                scanf("%d%d",&x,&y);
                update(l[x],r[x],y-a[x],1,n,1);
                a[x]=y;
            }
            else
            {
                int x;
                scanf("%d",&x);
                //  cout<<l[x]<<" "<<r[x]<<endl;
                printf("%I64d\n",query(l[x],r[x],1,n,1));
            }
            // for(int i=0;i<n;i++)cout<<l[i]<<"*****"<<r[i]<<endl;
        }
    }
    return 0;
}
/********************

********************/

View Code