SOJ 1024. Magic Island

 1 #include <iostream>
 2 #include <vector>
 3 using namespace std;
 4 
 5 struct Edge {
 6     int to;
 7     int dis;
 8     Edge(int t = 0, int d = 0) {
 9         to = t;
10         dis = d;
11     }
12 };
13 
14 const int maxn = 10005;
15 
16 vector<Edge> cities[maxn];
17 bool visited[maxn];
18 int maxDis;
19 int dis;
20 
21 void init(int n) {
22     for (int i = 1; i <= n; i++) {
23         visited[i] = false;
24         cities[i].clear();
25     }
26 }
27 
28 void dfs(int from) {
29     for (int i = 0; i < cities[from].size(); i++) {
30         Edge & e = cities[from][i];
31         if (!visited[e.to]) {
32             visited[e.to] = true;
33             dis += e.dis;
34             maxDis = maxDis > dis ? maxDis : dis;
35             dfs(e.to);
36             visited[e.to] = false;
37             dis -= e.dis;
38         }
39     }
40 }
41 
42 int main() {
43     int n, m;
44     int from, to, dis;
45     while (cin >> n >> m) {
46         init(n);
47 
48         for (int i = 1; i < n; i++) {
49             cin >> from >> to >> dis;
50             cities[from].push_back(Edge(to, dis));
51             cities[to].push_back(Edge(from, dis));
52         }
53 
54         dis = 0;
55         maxDis = 0;
56         visited[m] = true;
57         dfs(m);
58 
59         cout << maxDis << endl;
60     }
61 
62     return 0;
63 }