Poj 1986 distance queries

Http://poj.org/problem? Id = 1986

The distance between two points in a tree. (Do not consider disconnections)

Question: LCA template question.

1 # include <iostream> 2 # include <algorithm> 3 # include <cstring> 4 # include <string> 5 # include <cstdio> 6 # include <cmath> 7 # include <queue> 8 # include <map> 9 # include <set> 10 11 # define EPS 1e-5 12 # define maxn 55555 13 # define maxm 111111 14 # define INF 1000000000 15 using namespace STD; 16 int n, m, Q; 17 struct edge 18 {19 int V, next, W; 20} es [maxm]; 21 int head [maxn], E; 22 int IDE, TMP Dfn; 23 int f [2 * maxn], Id [maxn], used [maxn], POS [maxn], DIS [maxn]; 24 int MI [2 * maxn] [18]; 25 26 void Init () 27 {28 memset (Head,-1, sizeof (head); 29 E = 0; 30 ide = tmpdfn = 0; 31 memset (used, 0, sizeof (used); 32 dis [1] = 0; 33} 34 35 void add (int u, int V, int W) 36 {37 es [e]. V = V; 38 es [e]. W = W; 39 es [e]. next = head [u]; 40 head [u] = e ++; 41} 42 void DFS (int u) 43 {44 used [u] = 1; 45 Int TMP = ++ tmpdfn; 46 f [++ Ide] = TMP; 47 ID [TMP] = u; 48 POS [u] = ide; 49 for (INT I = head [u]; I! =-1; I = es [I]. Next) 50 {51 int v = es [I]. V; 52 If (! Used [v]) 53 {54 dis [v] = dis [u] + ES [I]. w; 55 DFS (V); 56 F [++ Ide] = TMP; 57} 58} 59 60} 61 void rmqinit (int n, int * W) 62 {63 for (INT I = 1; I <= N; I ++) MI [I] [0] = W [I]; 64 int M = (INT) (log (N * 1.0)/log (2.0); 65 for (INT I = 1; I <= m; I ++) 66 for (Int J = 1; j <= N; j ++) 67 {68 MI [J] [I] = mi [J] [I-1]; 69 If (J + (1 <(I-1) <= N) MI [J] [I] = min (MI [J] [I], mi [J + (1 <(I-1)] [I-1]); 70} 71} 72 73 int rmqmin (INT L, int R) 74 {75 int M = (INT) (log (R-l + 1) * 1.0)/log (2.0 )); 76 return min (MI [l] [m], MI [R-(1 <m) + 1] [m]); 77} 78 79 int LCA (INT l, int R) 80 {81 If (Pos [l]> POS [R]) Swap (L, R); 82 int ans = rmqmin (Pos [L], pos [R]); 83 return ID [ANS]; 84} 85 int main () 86 {87 // freopen ("/users/Apple/desktop/question/poj 1986_1/poj 1986_1/in", "r", stdin ); 88 scanf ("% d", & N, & M); 89 int U, V, W, L, R; 90 Init (); 91 while (M --) 92 {93 scanf ("% d % * s", & U, & V, & W); 94 add (U, V, W ); 95 Add (v, U, W); 96} 97 DFS (1); 98 rmqinit (IDE, f); 99 scanf ("% d", & Q ); 100 while (Q --) 101 {102 scanf ("% d", & L, & R); 103 printf ("% d \ n ", dis [l] + dis [R]-2 * Dis [LCA (L, R)]); 104} 105 return 0; 106}

 

Poj 1986 distance queries