Kefa and Park

最新推荐文章于 2022-05-27 22:51:17 发布

转载最新推荐文章于 2022-05-27 22:51:17 发布 · 55 阅读

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原文链接：http://www.cnblogs.com/superxuezhazha/p/5277688.html

本文探讨了CodeForces上的一道题目“Kefa and Park”，该题要求计算从Kefa家到公园内各餐厅的路径中连续含有猫的顶点数不超过m的所有可能路径数量。文章提供了一个C++实现方案，利用深度优先搜索（DFS）遍历树形结构，通过递归计算符合条件的路径。

#include<bits/stdc++.h>
#define max 100005
using namespace std;
int cats[max];
vector<int>tree[max];
int visit[max];
int ans=0;
int n,m;
vector<int>::iterator it;
void init()
{
    ans=0;
    memset(visit,0,sizeof(visit));
    for(int i=0;i<n;i++)
        tree[i].clear();
    memset(cats,0,sizeof(cats));
}
void dfs(int node,int cat)
{
    //cout<<"zhuangtai"<<node<<" "<<cat<<tree[node].size()<<"  "<<endl;
    visit[node]=1;
    if(cat>m) return;
    else
    {
        //cout<<"jiancha"<<node<<"  "<<cat<<"  "<<tree[node].size()<<endl;

        //if(tree[node].size()==1&&node!=1)
        //{
            //cout<<"shenegui"<<node<<"  "<<cat<<endl;
            //ans++;
        //}
        bool ok=1;
        for(int i=0;i<tree[node].size();i++)
        {
            if(!visit[tree[node][i]])
            {
                ok=0;
                //visit[tree[node][i]]=1;
                if(cats[tree[node][i]])
                    dfs(tree[node][i],cat+cats[tree[node][i]]);
                else dfs(tree[node][i],0);
            }
            //ans++;
        }
        //for(it=tree[node].begin();it!=tree[node].end();it++){
          //  if(!visit[*it]){
            //    if
            //}
        //}
        ans+=ok;
    }
}
/*4 1
1 1 0 0
1 2
1 3
1 4



7 1
1 0 1 1 0 0 0
1 2
1 3
2 4
2 5
3 6
3 7


3 2
1 1 1
1 2
2 3
*/
int main()
{

    while(scanf("%d%d",&n,&m)!=EOF)
    {
        init();
        for(int i=1;i<=n;i++)
        {
            cin>>cats[i];
        }
        int a,b;
        //cout<<"ok"<<endl;
        for(int i=1;i<n;i++)
        {
            scanf("%d%d",&a,&b);
            tree[a].push_back(b);
            tree[b].push_back(a);
        }
        visit[1]=1;
        dfs(1,cats[1]);
        if(ans==0) cout<<0<<endl;
        else
            cout<<ans<<endl;
    }
    return 0;
}

View Code

B - Kefa and Park

Time Limit:2000MS Memory Limit:262144KB 64bit IO Format:%I64d & %I64u

Submit Status Practice CodeForces 580C

Description

Kefa decided to celebrate his first big salary by going to the restaurant.

He lives by an unusual park. The park is a rooted tree consisting of n vertices with the root at vertex 1. Vertex 1 also contains Kefa's house. Unfortunaely for our hero, the park also contains cats. Kefa has already found out what are the vertices with cats in them.

The leaf vertices of the park contain restaurants. Kefa wants to choose a restaurant where he will go, but unfortunately he is very afraid of cats, so there is no way he will go to the restaurant if the path from the restaurant to his house contains more than mconsecutive vertices with cats.

Your task is to help Kefa count the number of restaurants where he can go.

Input

The first line contains two integers, n and m (2 ≤ n ≤ 10⁵, 1 ≤ m ≤ n) — the number of vertices of the tree and the maximum number of consecutive vertices with cats that is still ok for Kefa.

The second line contains n integers a₁, a₂, ..., a_n, where each a_i either equals to 0 (then vertex i has no cat), or equals to 1 (then vertex i has a cat).

Next n - 1 lines contains the edges of the tree in the format "x_iy_i" (without the quotes) (1 ≤ x_i, y_i ≤ n, x_i ≠ y_i), where x_i and y_i are the vertices of the tree, connected by an edge.

It is guaranteed that the given set of edges specifies a tree.

Output

A single integer — the number of distinct leaves of a tree the path to which from Kefa's home contains at most m consecutive vertices with cats.

Sample Input

Input

Output

Input

7 1
1 0 1 1 0 0 0
1 2
1 3
2 4
2 5
3 6
3 7

Output

Hint

Let us remind you that a tree is a connected graph on n vertices and n - 1 edge. A rooted tree is a tree with a special vertex called root. In a rooted tree among any two vertices connected by an edge, one vertex is a parent (the one closer to the root), and the other one is a child. A vertex is called a leaf, if it has no children.

Note to the first sample test: $\text{[math]}$ The vertices containing cats are marked red. The restaurants are at vertices 2, 3, 4. Kefa can't go only to the restaurant located at vertex 2.

Note to the second sample test: $\text{[math]}$ The restaurants are located at vertices 4, 5, 6, 7. Kefa can't go to restaurants 6, 7.

转载于:https://www.cnblogs.com/superxuezhazha/p/5277688.html