P3258 [JLOI2014]松鼠的新家 (简单的点差分)

https://www.luogu.org/problemnew/show/P3258

注意开始和最后结尾

 #include <bits/stdc++.h>
 #define read read()
 #define up(i,l,r) for(register int i = (l);i <= (r);i++)
 #define down(i,l,r) for(register int i = (l);i >= (r);i--)
 #define traversal_vedge(i) for(register int i = head[u]; i ;i = e[i].nxt)
 #define ll long long
 using namespace std;
 int read
 {
     int x = , f = ; char ch = getchar();
     while(ch <  || ch > ) {if(ch == '-')f = -; ch = getchar();}
     while(ch >= && ch <=) {x =  * x + ch - ;ch = getchar();}
     return x * f;
 }
 //--------------------------------------------------------------------
 const int N = ;
 int n,a[N];
 struct edge{
     int v,nxt;
 }e[N<<]; int tot,head[N];
 void add(int u,int v) {e[++tot] = (edge){v,head[u]};head[u] = tot;}

 int dep[N],size[N],fa[N],top[N];
 int cnt[N];

 void dfs(int u)
 {
     dep[u] = dep[fa[u]]+;
     size[u] = ;
     top[u] = u;
     int hson_id = ,hson_size = ;
     traversal_vedge(i)
     {
         int v = e[i].v;
         if(v == fa[u]) continue;
         fa[v] = u;
         dfs(v);
         size[u] += size[v];
         if(size[v] > hson_size) hson_id = v,hson_size = size[v];
     }
     if(hson_id) top[hson_id] = u;
 }

 int find(int u)
 {
     if(top[u] == u) return u;
     top[u] = find(top[u]);
     return top[u];
 }

 int lca(int x,int y)
 {
     if(find(x) != find(y))
     {
         if(dep[top[x]] > dep[top[y]]) return lca(fa[top[x]],y);
         else return lca(x,fa[top[y]]);
     }
     return dep[x] > dep[y] ? y : x;
 }

 void dfs_tree(int u)
 {
     traversal_vedge(i)
     {
         int v = e[i].v;
         if(v == fa[u]) continue;
         dfs_tree(v);
         cnt[u] += cnt[v];
     }
 }

 void readdata()
 {
     n = read;
     up(i,,n) a[i] = read;
     up(i,,n-)
     {
         int u = read, v = read;
         add(u,v);
         add(v,u);
     }
     dfs();
     up(i,,n-)
     {
         int u = a[i], v = a[i+];
         //cnt[u]++;
         cnt[fa[u]]++;
         cnt[v]++;
         int LCA = lca(u,v);
         cnt[LCA]--; cnt[fa[LCA]]--;
     }
     dfs_tree();
     up(i,,n)
     {
         if(i == a[]) cnt[i]++;
         else if(i == a[n]) cnt[i]--;
         printf("%d\n",cnt[i]);
     }
 }

 int main()
 {
     readdata();
     return ;
 }