最短路算法

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<queue>
 4 #include<stack>
 5 #include<cstring>
 6 #include<algorithm>
 7 
 8 using namespace std;
 9 #define INF 99999999
10 #define N 501
11 int g[N][N];
12 int d[N];
13 int n,m,w;
14 
15 bool BELLMAN_FORD()
16 {
17     for (int i=0;i<n;i++)
18         d[i]=INF;
19     d[0]=0;
20     for (int k=0;k<n-1;k++)
21         for (int i=0;i<n;i++)
22             for (int j=0;j<n;j++)
23                 if ((g[i][j]!=INF)&&(d[j]>d[i]+g[i][j]))
24                     d[j]=d[i]+g[i][j];
25     for (int i=0;i<n;i++)
26         for (int j=0;j<n;j++)
27             if ((g[i][j]!=INF)&&(d[j]>d[i]+g[i][j])) return false;
28     return true;
29 }
30 int main()
31 {
32     int _count;
33     scanf("%d",&_count);
34     for (int q=0;q<_count;q++)
35     {
36         scanf("%d%d%d",&n,&m,&w);
37         for (int i=0;i<n;i++)
38             for (int j=0;j<n;j++)
39                 g[i][j]=INF;
40         int u,v,t;
41         for (int i=0;i<m;i++)
42         {
43             scanf("%d%d%d",&u,&v,&t);
44             if (g[u-1][v-1]>t) g[u-1][v-1]=t;
45             if (g[v-1][u-1]>t) g[v-1][u-1]=t;
46         }
47         for (int i=0;i<w;i++)
48         {
49             scanf("%d%d%d",&u,&v,&t);
50             g[u-1][v-1]=-t;
51         }
52         if (BELLMAN_FORD()) printf("NO\n");
53         else printf("YES\n");
54     }
55     return 0;
56 }