codeforces 580 C. Kefa and Park

2015-12-05 · 1 min read · dfs tree

http://codeforces.com/contest/580/problem/C

题意：给出一棵树。每个叶子节点上有一个饭店。某些节点上有cat.现在问从根节点出发可以到达多少个饭店，保证在到达饭店的路径中补连续遇到m个以上的cat.

思路：建图，然后dfs..判断为叶子节点（饭店）的方法是某个点的叶子节点数为0.

/* ***********************************************
Author :111qqz
Created Time :2015年12月05日 星期六 10时17分01秒
File Name :580C.cpp
************************************************ */

 1#include <cstdio>
 2#include <cstring>
 3#include <iostream>
 4#include <algorithm>
 5#include <vector>
 6#include <queue>
 7#include <set>
 8#include <map>
 9#include <string>
10#include <cmath>
11#include <cstdlib>
12#include <ctime>
13#define fst first
14#define sec second
15#define lson l,m,rt<<1
16#define rson m+1,r,rt<<1|1
17#define ms(a,x) memset(a,x,sizeof(a))
18typedef long long LL;

1using namespace std;
2const double eps = 1E-8;
3const int dx4[4]={1,0,0,-1};
4const int dy4[4]={0,-1,1,0};
5const int inf = 0x3f3f3f3f;
6const int N=1E5+7;

1int m,n;
2bool vis[N];
3vector<int>edge[N];
4int hascat[N];
5int ans;

1void dfs( int cur,int num)
2{
3    vis[cur] = true;
4    if (hascat[cur])
5	num++;
6    else num = 0 ;

 //   cout<<"cur:"<<cur<<" num:"<<num<<endl;

    if (num>m) return;

 1    int leafnum = 0;
 2    for ( int i = 0 ; i <edge[cur].size(); i++ )
 3    {
 4	int v = edge[cur][i];
 5//	cout<<"cur:"<<cur<<" v:"<<v<<endl;
 6	if (!vis[v])
 7	{
 8	    dfs(v,num);
 9	    leafnum++;
10	}
11    }
12    if (leafnum==0) ans++;

 1}
 2int main()
 3{
 4	#ifndef  ONLINE_JUDGE 
 5	freopen("code/in.txt","r",stdin);
 6	#endif
 7    ms(vis,false);
 8    ms(hascat,0);
 9    scanf("%d %d",&n,&m);
10    for ( int i =  1 ; i <= n ; i++) scanf("%d",&hascat[i]);
11    for ( int i = 1  ; i <= n-1 ; i++)
12    {
13	int u,v;
14	scanf("%d %d",&u,&v);
15	edge[u].push_back(v);
16	edge[v].push_back(u);
17    }

1    ans = 0 ;
2    dfs(1,0);
3    printf("%d\n",ans);

1  #ifndef ONLINE_JUDGE  
2  fclose(stdin);
3  #endif
4    return 0;
5}