codeforces 580C Kefa and Park（DFS）

题目链接：http://codeforces.com/contest/580/problem/C

#include<cstdio>
#include<vector>
#include<cstring>
#define MAX 100010
using namespace std;
vector <int> a[MAX];
int visit[MAX];
int cat[MAX];
int leaf[MAX];
int ans,m;
void dfs(int x,int numcat)
{
    if(visit[x])
    return;
    else
    visit[x]=1;
    if(cat[x])
    numcat++;
    else
    numcat=0;
    if(numcat>m)
    return;
    if(leaf[x]==1&&x!=1)
    ans++;
    int len=a[x].size();
    for(int i=0;i<len;i++)
    dfs(a[x][i],numcat);
}
int main()
{
    int n,i,j,k,numcat;
    while(~scanf("%d%d",&n,&m))
    {
        numcat=ans=0;
        memset(visit,0,sizeof(visit));
        memset(leaf,0,sizeof(leaf));
        for(i=1;i<=n;i++)
        {
            scanf("%d",&cat[i]);
            a[i].clear();
        }
        for(i=1;i<=n-1;i++)
        {
            scanf("%d%d",&j,&k);
            a[j].push_back(k);
            a[k].push_back(j);
            leaf[j]++;
            leaf[k]++;
        }
        dfs(1,0);
        printf("%d\n",ans);
    }
    return 0;
}