《数据结构与算法分析：C语言描述》复习——第九章“图论”——多源最短路径问题

 1 // A simple illustration for all pairs shortest path using Floyd Algorithm.
 2 #include <iostream>
 3 #include <vector>
 4 using namespace std;
 5 
 6 const int INFINITY = 1000000000;
 7 
 8 void floydAlgorithm(const vector<vector<int> > &graph, 
 9     vector<vector<int> > &dist)
10 {
11     int n;
12     int i, j, k;
13     
14     n = (int)graph.size();
15     dist.resize(n);
16     for (i = 0; i < n; ++i) {
17         dist[i].resize(n, INFINITY);
18     }
19     
20     for (i = 0; i < n; ++i) {
21         for (j = 0; j < n; ++j) {
22             dist[i][j] = graph[i][j];
23         }
24     }
25     
26     for (k = 0; k < n; ++k) {
27         for (i = 0; i < n; ++i) {
28             for (j = 0; j < n; ++j) {
29                 if (dist[i][k] + dist[k][j] >= dist[i][j]) {
30                     continue;
31                 }
32                 dist[i][j] = dist[i][k] + dist[k][j];
33             }
34         }
35     }
36 }
37 
38 int main()
39 {
40     vector<vector<int> > graph;
41     vector<vector<int> > dist;
42     int n;
43     int nk;
44     int i, j;
45     int tmp, tmp_dist;
46     
47     while (cin >> n && n > 0) {
48         graph.resize(n);
49         for (i = 0; i < n; ++i) {
50             graph[i].resize(n, INFINITY);
51         }
52         
53         for (i = 0; i < n; ++i) {
54             cin >> nk;
55             for (j = 0; j < nk; ++j) {
56                 cin >> tmp >> tmp_dist;
57                 graph[i][tmp] = tmp_dist;
58             }
59         }
60         
61         floydAlgorithm(graph, dist);
62         
63         for (i = 0; i < n; ++i) {
64             for (j = 0; j < n; ++j) {
65                 cout << "[" << i << "][" << j << "]: ";
66                 if (dist[i][j] < INFINITY) {
67                     cout << dist[i][j] << endl;
68                 } else {
69                     cout << "Unreachable" << endl;
70                 }
71             }
72         }
73         
74         for (i = 0; i < n; ++i) {
75             graph[i].clear();
76         }
77         graph.clear();
78         
79         for (i = 0; i < n; ++i) {
80             dist[i].clear();
81         }
82         dist.clear();
83     }
84     
85     return 0;
86 }