ccf算法模板

bellman ford 算法求最短路径

 1 #include <iostream>
 2 using namespace std;
 3 const int maxnum = 100;
 4 const int maxint = 99999;
 5 
 6 // 边，
 7 typedef struct Edge{
 8     int u, v;    // 起点，重点
 9     int weight;  // 边的权值
10 }Edge;
11 
12 Edge edge[maxnum];     // 保存边的值
13 int  dist[maxnum];     // 结点到源点最小距离
14 
15 int nodenum, edgenum, source;    // 结点数，边数，源点
16 
17 // 初始化图
18 void init()
19 {
20     // 输入结点数，边数，源点
21     cin >> nodenum >> edgenum >> source;
22     for (int i = 1; i <= nodenum; ++i)
23         dist[i] = maxint;
24     dist[source] = 0;
25     for (int i = 1; i <= edgenum; ++i)
26     {
27         cin >> edge[i].u >> edge[i].v >> edge[i].weight;
28         if (edge[i].u == source)          //注意这里设置初始情况
29             dist[edge[i].v] = edge[i].weight;
30     }
31 }
32 
33 // 松弛计算
34 void relax(int u, int v, int weight)
35 {
36     if (dist[v] > dist[u] + weight)
37         dist[v] = dist[u] + weight;
38 }
39 
40 bool Bellman_Ford()
41 {
42     for (int i = 1; i <= nodenum - 1; ++i)
43     for (int j = 1; j <= edgenum; ++j)
44         relax(edge[j].u, edge[j].v, edge[j].weight);
45     bool flag = 1;
46     // 判断是否有负环路
47     for (int i = 1; i <= edgenum; ++i)
48     if (dist[edge[i].v] > dist[edge[i].u] + edge[i].weight)
49     {
50         flag = 0;
51         break;
52     }
53     return flag;
54 }
55 int main()
56 {
57     //freopen("input3.txt", "r", stdin);
58     init();
59     if (Bellman_Ford())
60     for (int i = 1; i <= nodenum; i++)
61         cout << dist[i] << endl;
62     return 0;
63 }