NC 15158. Little H and games

Link
meaning:
bombing a certain point on the tree diagram will affectthe point \ (q \) bombingsthat are not more than \ (2 \) away from the point, each time the idea of ​​the number of damages to this point must be output : Let \ (tot [x] [0] \) bethe number of damagesto \ (x \) , \ (tot [x] [1] \) tothe number of damages to the childof \ (x \) , \ (tot [x] [2] \) The number of times the child ’s child is damagedIf the bombing \ (x \) : \ (x \) ’s father ’s father is damaged: \ (tot [fa [fa [x]]] [0 ] ++ \) \ (x \) 's father is damaged: \ (tot [fa [x]] [0] ++ \) \ (x \) and \ (x \) ' s brother is damaged: \ (tot [fa [x]] [1] ++ \) \ (x \) 's child is damaged: \ (tot [x] [1] ++ \) \ (x \) ' s child's child is damaged: \ ( tot [x] [2] ++ \) \ (x \)









The total number of damages is: \ (tot [x] [0] + tot [fa [x]] [1] + tot [fa [fa [x]]] [2] \)
Code:

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
typedef long long ll;
typedef pair<int,int> pii;
//head
const int N=750005;
vector<int>g[N];
int fa[N],tot[N][3];
void dfs(int u) {
    for(auto v:g[u]) {
        if(v==fa[u]) continue;
        fa[v]=u;
        dfs(v);    
    }
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n,q;
    cin>>n>>q;
    for(int i=1;i<n;i++) {
        int u,v;
        cin>>u>>v;
        g[u].pb(v);
        g[v].pb(u);
    }
    dfs(1);
    for(int i=1;i<=q;i++) {
    	int x;
    	cin>>x;
    	tot[x][1]++,tot[x][2]++;
    	if(fa[fa[x]]) tot[fa[fa[x]]][0]++;
    	if(fa[x]) tot[fa[x]][0]++,tot[fa[x]][1]++;
    	else tot[x][0]++;
    	cout<<tot[x][0]+tot[fa[x]][1]+tot[fa[fa[x]]][2]<<endl;
    }
    return 0;
}