ACM学习历程—HDU 5326 Work（树形递推）

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <string>
#include <algorithm>
#define LL long long

using namespace std;

const int maxN = 105;

struct Edge
{
    int to, next;
}edge[maxN];

int head[maxN], cnt;

void addEdge(int u, int v)
{
    edge[cnt].to = v;
    edge[cnt].next = head[u];
    head[u] = cnt;
    cnt++;
}

void initEdge()
{
    memset(head, -1, sizeof(head));
    cnt = 0;
}

int n, k;
int fa[maxN], p[maxN];

void input()
{
    initEdge();
    memset(p, -1, sizeof(p));
    int u, v;
    for (int i = 1; i < n; ++i)
    {
        scanf("%d%d", &u, &v);
        addEdge(u, v);
    }
}


void dfs(int now)
{
    p[now] = 0;
    int to;
    for (int i = head[now]; i != -1; i = edge[i].next)
    {
        to = edge[i].to;
        if (p[to] == -1)
            dfs(to);
        p[now] += p[to]+1;
    }
}

void work()
{
    int ans = 0;
    for (int i = 1; i <= n; ++i)
    {
        if (p[i] != -1)
        {
            if (p[i] == k)
                ans++;
        }
        else
        {
            dfs(i);
            if (p[i] == k)
                ans++;
        }
    }
    printf("%d\n", ans);
}

int main()
{
    //freopen("test.in", "r", stdin);
    while (scanf("%d%d", &n, &k) != EOF)
    {
        input();
        work();
    }
    return 0;
}