poj 1741

#include <iostream>
#include <algorithm>
#include <cstring>
#include <string>
#include <cstdio>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#define eps 1e-5
#define MAXN 11111
#define MAXM 55555
#define INF 1000000000
using namespace std;
struct EDGE
{
    int v, next, w;
}edge[MAXM];
int head[MAXN], e;
int n, k, vis[MAXN], ans, root, num;
void init()
{
    memset(vis, 0, sizeof(vis));
    memset(head, -1, sizeof(head));
    e = ans = 0;
}
void add(int u, int v, int w)
{
    edge[e].v = v;
    edge[e].w = w;
    edge[e].next = head[u];
    head[u] = e++;
}
int mx[MAXN], size[MAXN], mi, dis[MAXN];
void dfssize(int u, int fa) //处理子树的大小
{
    size[u] = 1;
    mx[u] = 0;
    for(int i = head[u]; i != -1; i = edge[i].next)
    {
        int v = edge[i].v;
        if(v != fa && !vis[v])
        {
            dfssize(v, u);
            size[u] += size[v];
            if(size[v] > mx[u]) mx[u] = size[v];
        }
    }
}
void dfsroot(int r, int u, int fa) //求重心
{
    if(size[r] - size[u] > mx[u]) mx[u] = size[r] - size[u];
    if(mx[u] < mi) mi = mx[u], root = u;
    for(int i = head[u]; i != -1; i = edge[i].next)
    {
        int v = edge[i].v;
        if(v != fa && !vis[v]) dfsroot(r, v, u);
    }
}
void dfsdis(int u, int d, int fa) //求距离
{
    dis[num++] = d;
    for(int i = head[u]; i != -1; i = edge[i].next)
    {
        int v = edge[i].v;
        if(v != fa && !vis[v]) dfsdis(v, d + edge[i].w, u);
    }
}
int calc(int u, int d)
{
    int ret = 0;
    num = 0;
    dfsdis(u, d, 0);
    sort(dis, dis + num);
    int i = 0, j = num - 1;
    while(i < j) //二分求之
    {
        while(dis[i] + dis[j] > k && i < j) j--;
        ret += j - i;
        i++;
    }
    return ret;
}
void dfs(int u)
{
    mi = n;
    dfssize(u, 0);
    dfsroot(u, u, 0);
    ans += calc(root, 0);
    vis[root] = 1;
    printf("root==%d\n",root);
    for(int i = head[root]; i != -1; i = edge[i].next)
    {
        int v = edge[i].v;
        if(!vis[v])
        {
            ans -= calc(v, edge[i].w);
            dfs(v);
        }
    }
}
int main()
{
    while(scanf("%d%d", &n, &k) != EOF)
    {
        if(!n && !k) break;
        init();
        int u, v, w;
        for(int i = 0; i < n - 1; i++)
        {
            scanf("%d%d%d", &u, &v, &w);
            add(u, v, w);
            add(v, u, w);
        }
        dfs(1);
        printf("%d\n", ans);
    }
    return 0;
}