Ccf-csp 202112-5 extreme path violence 12 points

Original link ：CCF-CSP 202112-5 Range path

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N=5e5+10;

int n,k1,k2;
vector<int> g[N];
vector<int> v;
int vis[N];
set<pair<int,int>> res;

void dfs(int x,vector<int>& v,int y)
{
    
    int minnum=min(x,y)-k1;
    int maxnum=max(x,y)+k2;
    int minp=*(min_element(v.begin(),v.end()));
    int maxp=*(max_element(v.begin(),v.end()));
    if(minnum<=minp && minp<=maxp && maxp<=maxnum)
    {
    
        int a=x,b=y;
        if(a>b) swap(a,b);
        pair<int,int> p=make_pair(a,b);
        res.insert(p);
    }
    for(int i=0;i<g[y].size();i++)
    {
    
        int tmp=g[y][i];
        if(vis[tmp]==0)
        {
    
            v.push_back(tmp);
            vis[tmp]=1;
            dfs(x,v,tmp);
            v.pop_back();
            vis[tmp]=0;
        }
    }
}

int main()
{
    
    std::ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cin>>n>>k1>>k2;
    if(n<=5000)
    {
    
        for(int i=0;i<n-1;i++)
        {
    
            int x,y;
            cin>>x>>y;
            g[x].push_back(y);
            g[y].push_back(x);
        }
        for(int i=1;i<=n;i++)
        {
    
           memset(vis,0,sizeof(vis));
           v.clear();
           v.push_back(i);
           vis[i]=1;
           dfs(i,v,i);
        }
        cout<<res.size()<<endl;
    }
    return 0;
}