【SPFA】POJ3259-Wormhole

普通的SPFA的负环判定。犯了三个错误，全部写在注释里了。

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<queue>
 5 #include<algorithm>
 6 using namespace std;
 7 const int MAXNm=10000+500;
 8 const int MAXNn=500+50;
 9 const int INF=0x7fffffff;
10 int n,m,ww;
11 int u[MAXNm],v[MAXNm],w[MAXNm];
12 int first[MAXNn],next[MAXNm];
13 int dis[MAXNn];
14 void addedge(int tu,int num)
15 {
16     next[num]=first[tu];
17     first[tu]=num;
18 }
19
20 int SPFA()
21 {
22     queue<int> que;
23     int vis[MAXNn],appear[MAXNn];
24     que.push(0);
25     for (int i=0;i<n;i++)
26     {
27         dis[i]=INF;
28         vis[i]=0;
29         appear[i]=0;
30     }
31     /*不要遗漏了上述初始化步骤*/
32     dis[0]=0;
33     vis[0]=1;
34     appear[0]=1;
35
36     while (!que.empty())
37     {
38         int head=que.front();
39         que.pop();
40         vis[head]=0;
41         /*注意这里vis[head]要重归于零！很容易错写成vis[k]=0*/
42         int k=first[head];
43         while (k!=-1)
44         {
45             if (dis[v[k]]>dis[u[k]]+w[k])
46             {
47                 dis[v[k]]=dis[u[k]]+w[k];
48                 if (!vis[v[k]])
49                 /*不要把vis[v[k]]写成vis[k]了*/
50                 {
51                     appear[v[k]]++;
52                     vis[v[k]]=1;
53                     que.push(v[k]);
54                 }
55                 if (appear[v[k]]>=n) return 0;
56             }
57             k=next[k];
58         }
59     }
60     return 1;
61 }
62
63 int main()
64 {
65     int c;
66     scanf("%d",&c);
67     for (int kase=0;kase<c;kase++)
68     {
69         scanf("%d%d%d",&n,&m,&ww);
70         for (int i=0;i<n;i++) first[i]=-1;
71
72         for (int i=0;i<m;i++)
73         {
74             scanf("%d%d%d",&u[i],&v[i],&w[i]);
75             u[i]--;
76             v[i]--;
77             addedge(u[i],i);
78             u[i+m]=v[i];
79             v[i+m]=u[i];
80             w[i+m]=w[i];
81             addedge(u[i+m],i+m);
82         }
83         for (int i=2*m;i<2*m+ww;i++)
84         {
85             scanf("%d%d%d",&u[i],&v[i],&w[i]);
86             u[i]--;
87             v[i]--;
88             w[i]=-w[i];
89             addedge(u[i],i);
90         }
91         if (!SPFA()) cout<<"YES";else cout<<"NO";cout<<endl;
92     }
93
94     return 0;
95 }