uva 10938(dfs)

题意：在一棵树上求距离中点，若距离是奇数则输出中间两个点。

思路：看到题意第一反应是lca，再看一下数据量那么小。。。一定有什么简单的做法。其实只要dfs一下就可以了保存路径输出中间的两个点。

代码如下：

 1 /**************************************************
 2  * Author     : xiaohao Z
 3  * Blog     : http://www.cnblogs.com/shu-xiaohao/
 4  * Last modified : 2014-02-05 18:39
 5  * Filename     : uva_10938.cpp
 6  * Description     : 
 7  * ************************************************/
 8 
 9 #include <iostream>
10 #include <cstdio>
11 #include <cstring>
12 #include <cstdlib>
13 #include <cmath>
14 #include <algorithm>
15 #include <queue>
16 #include <stack>
17 #include <vector>
18 #include <set>
19 #include <map>
20 #define MP(a, b) make_pair(a, b)
21 #define PB(a) push_back(a)
22 
23 using namespace std;
24 typedef long long ll;
25 typedef pair<int, int> pii;
26 typedef pair<unsigned int,unsigned int> puu;
27 typedef pair<int, double> pid;
28 typedef pair<ll, int> pli;
29 typedef pair<int, ll> pil;
30 
31 const int INF = 0x3f3f3f3f;
32 const double eps = 1E-6;
33 const int LEN = 10100;
34 vector<int> Map[LEN];
35 int n, vis[LEN], path[LEN], ed;
36 
37 void dfs(int v, int dep)
38 {
39     vis[v] = 1;
40     path[dep] = v;
41     if(v == ed){
42          if(dep%2==0) printf("The fleas meet at %d.\n", path[dep/2]);
43          else printf("The fleas jump forever between %d and %d.\n", min(path[dep/2], path[dep/2+1]), max(path[dep/2], path[dep/2+1]));
44     }
45     for(int i=0; i<Map[v].size(); i++){
46          if(!vis[Map[v][i]]) dfs(Map[v][i], dep+1);
47     }
48 }
49 int main()
50 {
51 //    freopen("in.txt", "r", stdin);
52 
53     int a, b, st;
54     while(scanf("%d", &n)!=EOF && n){
55         for(int i=0; i<LEN; i++)Map[i].clear();
56         for(int i=0; i<n-1; i++){
57              scanf("%d%d", &a, &b);
58              Map[a].PB(b);
59              Map[b].PB(a);
60         }
61         int q;
62         scanf("%d", &q);
63         for(int i=0; i<q; i++){
64              scanf("%d%d", &st, &ed);
65              memset(vis, 0, sizeof vis);
66              memset(path, 0, sizeof path);
67              dfs(st, 0);
68         }
69     }
70     return 0;
71 }
View Code

 

posted @ 2014-02-05 19:06  张小豪  阅读(148)  评论(0)  编辑  收藏  举报