POJ1741

师爷：你叫张麻子？可你脸上没麻子啊！张麻子：黄四郎脸上有四吗？

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
const int N = 30000;
int key[N], next[N], len[N], head[N], cnt, d[N], s[N], q[N], t, a[N], a_c, f[N], dist, ans, n;
bool no[N];
inline void add (int x, int y, int w)
{
    key[cnt] = y;
    next[cnt] = head[x];
    len[cnt] = w;
    head[x] = cnt ++;
}
inline void DFS (int x, int fa)
{
    s[x] = 1;
    f[x] = 0;
    q[++ t] = x;
    for (int i = head[x]; ~ i; i = next[i])
        if (key[i] != fa && !no[key[i]])
        {
            DFS (key[i], x);
            s[x] += s[key[i]];
            f[x] = max (f[x], s[key[i]]);
        }
}
inline int findroot (int S)
{
    t = 0;int t1 = 0x3f3f3f3f, t2 = 0;
    DFS (S, 0);
    for (int i = 1; i <= t; i ++)
    {
        int t = max (f[q[i]], s[S] - s[q[i]]);
        if (t < t1)
            t1 = t, t2 = q[i];
    }
    return t2;
}
inline void getdis (int x, int fa)
{
    a[++ a_c] = d[x];
    for (int i = head[x]; ~ i; i = next[i])
        if (key[i] != fa && !no[key[i]])
        {
            d[key[i]] = d[x] + len[i];
            
            getdis (key[i], x);
        }
    
}
inline void getpoint (int x, int fa)
{
    a[++ a_c] = d[x];
    for (int i = head[x]; ~ i; i = next[i])
        if (key[i] != fa && !no[key[i]])
            getpoint (key[i], x);
}
inline int slide ()
{
    int z (0);
    sort (a + 1, a + 1 + a_c);
    for (int i = 1, j = a_c; i <= a_c && i < j; i ++)
    {
        for (; a[i] + a[j] > dist && j > i; j --);
        z += j - i;
    }
    return z;
}
inline void calc (int rt)
{
    d[rt] = 0;a_c = 0;
    getdis (rt, 0);
    ans += slide ();
    for (int i = head[rt]; ~ i; i = next[i])
        if (!no[key[i]])
        {
            a_c = 0;
            getpoint (key[i], rt);
            ans -= slide ();
        }
}
inline void F (int S)
{
    int rt = findroot (S);
    no[rt] = true;
    calc (rt);
    for (int i = head[rt]; ~ i; i = next[i])
        if (!no[key[i]])
            F (key[i]);
}
int main ()
{
    while (scanf ("%d%d", &n, &dist), n + dist)
    {
        ans = cnt = 0;
        memset (head, -1, sizeof head);
        memset (no, 0, sizeof no);
        for (int i = 1, a, b, c; i <= n - 1; i ++)
            scanf ("%d%d%d", &a, &b, &c), add (a, b, c), add (b, a, c);
        F (1);
        printf ("%d\n", ans);
    }
    return 0;
}