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？
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1 #include <iostream> 2 #include <cstdio> 3 #include <algorithm> 4 #include <cstring> 5 using namespace std; 6 const int N = 30000; 7 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; 8 bool no[N]; 9 inline void add (int x, int y, int w) 10 { 11 key[cnt] = y; 12 next[cnt] = head[x]; 13 len[cnt] = w; 14 head[x] = cnt ++; 15 } 16 inline void DFS (int x, int fa) 17 { 18 s[x] = 1; 19 f[x] = 0; 20 q[++ t] = x; 21 for (int i = head[x]; ~ i; i = next[i]) 22 if (key[i] != fa && !no[key[i]]) 23 { 24 DFS (key[i], x); 25 s[x] += s[key[i]]; 26 f[x] = max (f[x], s[key[i]]); 27 } 28 } 29 inline int findroot (int S) 30 { 31 t = 0;int t1 = 0x3f3f3f3f, t2 = 0; 32 DFS (S, 0); 33 for (int i = 1; i <= t; i ++) 34 { 35 int t = max (f[q[i]], s[S] - s[q[i]]); 36 if (t < t1) 37 t1 = t, t2 = q[i]; 38 } 39 return t2; 40 } 41 inline void getdis (int x, int fa) 42 { 43 a[++ a_c] = d[x]; 44 for (int i = head[x]; ~ i; i = next[i]) 45 if (key[i] != fa && !no[key[i]]) 46 { 47 d[key[i]] = d[x] + len[i]; 48 49 getdis (key[i], x); 50 } 51 52 } 53 inline void getpoint (int x, int fa) 54 { 55 a[++ a_c] = d[x]; 56 for (int i = head[x]; ~ i; i = next[i]) 57 if (key[i] != fa && !no[key[i]]) 58 getpoint (key[i], x); 59 } 60 inline int slide () 61 { 62 int z (0); 63 sort (a + 1, a + 1 + a_c); 64 for (int i = 1, j = a_c; i <= a_c && i < j; i ++) 65 { 66 for (; a[i] + a[j] > dist && j > i; j --); 67 z += j - i; 68 } 69 return z; 70 } 71 inline void calc (int rt) 72 { 73 d[rt] = 0;a_c = 0; 74 getdis (rt, 0); 75 ans += slide (); 76 for (int i = head[rt]; ~ i; i = next[i]) 77 if (!no[key[i]]) 78 { 79 a_c = 0; 80 getpoint (key[i], rt); 81 ans -= slide (); 82 } 83 } 84 inline void F (int S) 85 { 86 int rt = findroot (S); 87 no[rt] = true; 88 calc (rt); 89 for (int i = head[rt]; ~ i; i = next[i]) 90 if (!no[key[i]]) 91 F (key[i]); 92 } 93 int main () 94 { 95 while (scanf ("%d%d", &n, &dist), n + dist) 96 { 97 ans = cnt = 0; 98 memset (head, -1, sizeof head); 99 memset (no, 0, sizeof no); 100 for (int i = 1, a, b, c; i <= n - 1; i ++) 101 scanf ("%d%d%d", &a, &b, &c), add (a, b, c), add (b, a, c); 102 F (1); 103 printf ("%d\n", ans); 104 } 105 return 0; 106 }