Luogu P1600 Love Running a tree difference every day

Luogu P1600 love running every day

### trees differential

Topic Link
tree problem
I did not see how the difference
Conditions are observed two
lca front half (including lca) \ (D [S_i] -d [X] = W [X] \)
\ (D [I] \) represents the depth of the node
half after lca \ (D [S_i] + d [x]
-2 * d [lca (S_i, T_i)] = w [x] \) but how to achieve this equation? ?
Achieve \ (d [S_i] = w
[x] + d [x] \) can be converted to the segment tree merge model
in \ (S_i \) to (LCA \) \ increases on the path \ (d [S_i] \) value
last obtained for each point \ (w [x] + d [x] \) number value
, but seems a little less than the opening.
Vector can build a record run on each node
and a global array c
in the tree when recording dfs \ (c [w [x] + d [x]] \) recursively back when calculating the difference between the original and the answer .

---

code show as below:

#include<bits/stdc++.h>
#define mk make_pair
using namespace std;
const int maxn=300000;
int n,m,head[maxn],tot,w[maxn],lc[maxn],ans[maxn];
int id[maxn],d[maxn],fa[maxn],f[maxn],c1[maxn*2],c2[maxn*2];
struct node{
    int nxt,to;
    #define nxt(x) e[x].nxt
    #define to(x) e[x].to
}e[maxn<<1];
inline void add(int from,int to){
    to(++tot)=to;nxt(tot)=head[from];head[from]=tot;
}
inline int find(int x){return fa[x]==x ? fa[x] : fa[x]=find(fa[x]);}
vector<pair<int,int> > pt[maxn];
vector<int> a1[maxn],a2[maxn],b1[maxn],b2[maxn];
pair<int,int> di[maxn];
void tarjan(int x){
    id[x]=1;
    for(int i=head[x];i;i=nxt(i)){
        if(id[to(i)]) continue;
        d[to(i)]=d[x]+1;
        tarjan(to(i));
        fa[to(i)]=x;f[to(i)]=x;
    }
    for(unsigned int i=0;i<pt[x].size();i++){
        int to=pt[x][i].first,vl=pt[x][i].second;
        if(id[to]==2) lc[vl]=find(to);
    }
    id[x]=2;
}
void dfs(int x){
    int val1=c1[d[x]+w[x]],val2=c2[w[x]-d[x]+n];
    id[x]=1;
    for(int i=head[x];i;i=nxt(i)){
        if(id[to(i)]) continue;
        dfs(to(i));
    }
    for(int i=0;i<a1[x].size();i++)
        c1[a1[x][i]]++;
    for(int i=0;i<b1[x].size();i++)
        c1[b1[x][i]]--;
    for(int i=0;i<a2[x].size();i++)
        c2[n+a2[x][i]]++;
    for(int i=0;i<b2[x].size();i++)
        c2[n+b2[x][i]]--;
    ans[x]=c1[d[x]+w[x]]+c2[w[x]-d[x]+n]-val1-val2;
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1;i<n;i++){
        int x,y;scanf("%d%d",&x,&y);
        add(x,y);add(y,x);
    }
    for(int i=1;i<=n;i++) fa[i]=i,scanf("%d",&w[i]);
    for(int i=1;i<=m;i++){
        int x,y;scanf("%d%d",&x,&y);
        if(x==y) lc[i]=x;
        pt[x].push_back(mk(y,i));pt[y].push_back(mk(x,i));
        di[i].first=x;di[i].second=y;
    }
    d[1]=1;tarjan(1);
    for(int i=1;i<=m;i++){
        int x=di[i].first,y=di[i].second;
        a1[x].push_back(d[x]);a2[y].push_back(d[x]-2*d[lc[i]]);
        b1[f[lc[i]]].push_back(d[x]);b2[lc[i]].push_back(d[x]-2*d[lc[i]]);
    }
    memset(id,0,sizeof(id));
    dfs(1);
    for(int i=1;i<=n;i++) printf("%d ",ans[i]);
    return 0;
}