1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 // Artur Kraska, II UWr #include #define forr(i, n) for(int i=0; i=b; i--) #define MP make_pair #define PB push_back #define deb(X) X; #define M 1000000007 #define INF 1000000007LL using namespace std; int n, k, a, b, w, teraz; long long pot[100007]; vector wagi; vector > wektory; struct kraw { int dl; int cel; }; kraw kr; struct wierzch { vector l; int byl; }; wierzch tab[100007]; void dfs_wagi(int nr, int korzen, int dl, long long waga) { // cout << "wlazi do " << nr << endl; tab[nr].byl = teraz; waga += pot[dl-1]; if(nr > korzen) { wagi.PB(waga); } for(auto nb : tab[nr].l) { if(tab[nb.cel].byl != teraz) { dfs_wagi(nb.cel, korzen, nb.dl, waga); } } } void dfs_wektory(int nr, int korzen, int dl, vector v) { // cout << "wlazi do " << nr << endl; tab[nr].byl = teraz; vector v2(v); v2.PB(-dl); if(nr > korzen) { wektory.PB(v2); } for(auto nb : tab[nr].l) { if(tab[nb.cel].byl != teraz) { dfs_wektory(nb.cel, korzen, nb.dl, v2); } } } int main() { scanf("%d %d", &n, &k); int maxw = 0; forr(i, n-1) { scanf("%d %d %d", &a, &b, &w); maxw = max(w, maxw); kr.cel = b; kr.dl = w; tab[a].l.PB(kr); kr.cel = a; tab[b].l.PB(kr); } if(maxw <= 4) { pot[0] = 1; FOR(i, 1, n+1) pot[i] = pot[i-1]*n; FOR(i, 1, n-1) { teraz++; dfs_wagi(i, i, 1, -1); } sort(wagi.begin(), wagi.end()); // for(auto w : wagi) // cout << "waga: " << w*n << endl; printf("%lld\n", wagi[k-1]%M*n%M); } else { pot[0] = 1; FOR(i, 1, n+1) pot[i] = (pot[i-1]*n)%M; FOR(i, 1, n-1) { teraz++; vector v; dfs_wektory(i, i, 0, v); } FOREACH(it, wektory) { sort(it->begin(), it->end()); } sort(wektory.begin(), wektory.end()); /* for(auto v : wektory) { for(auto el : v) { cout << " " << el; } cout << endl; } */ long long res = M-1; for(auto el: wektory[n*(n-1)/2-k]) { res += pot[-el]; } printf("%lld\n", res%M); } return 0; }