uestc 方老师分身 I

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<cstring>
 5 #include<string>
 6 #include<queue>
 7 #include<algorithm>
 8 #include<map>
 9 #include<iomanip>
10 #include<climits>
11 #include<string.h>
12 #include<cmath>
13 #include<stdlib.h>
14 #include<vector>
15 #define INF 1e7
16 #define MAXN 100010
17 #define maxn 1000010
18 #define Mod 1000007
19 #define N 1010
20 using namespace std;
21 typedef long long LL;
22 
23 int n, m, x;
24 int G[N][N];
25 int d[N], d1[N], d2[N];
26 bool vis[N];
27 
28 bool Dijkstra(int x, int* d)
29 {
30     int i, j, pos, min;
31     for (i = 1; i <= n; ++i)
32         d[i] = G[x][i];
33     d[x] = 0;
34     vis[x] = true;
35     for (i = 1; i <= n; ++i) {
36         min = INF;
37         for (j = 1; j <= n; ++j) {
38             if (d[j] < min && !vis[j]) {
39                 pos = j;
40                 min = d[j];
41             }
42         }
43         if (min == INF) return false;
44         vis[pos] = true;
45         for (j = 1; j <= n; ++j)
46             if (d[pos] + G[pos][j] < d[j] && !vis[j])
47                 d[j] = d[pos] + G[pos][j];
48     }
49     return true;
50 }
51 
52 void process()
53 {
54     int u, v, t;
55     for (int i = 0; i <= n; ++i)
56         for (int j = 0; j <= n; ++j)
57             G[i][j] = INF;
58     for (int i = 0; i < m; ++i) {
59         cin >> u >> v >> t;
60         G[u][v] = t;
61     }
62     memset(vis, 0, sizeof(vis));
63     Dijkstra(x, d1);
64     for (int i = 0; i <= n; ++i)
65         for (int j = i + 1; j <= n; ++j)
66             swap(G[i][j], G[j][i]);
67     memset(vis, 0, sizeof(vis));
68     Dijkstra(x, d2);
69     for (int i = 0; i <= n; ++i)
70         d[i] = d1[i] + d2[i];
71     /*for (int i = 1; i <= n; ++i)
72         cout << d[i] << " ";
73     cout << endl;*/
74     int ans = 0;
75     for (int i = 1; i <= n; ++i)
76             ans = max(ans, d[i]);
77     cout << ans << endl;
78 }
79 
80 int main()
81 {
82     while (cin >> n >> m >> x)
83         process();
84     return 0;
85 }