Reward

http://acm.hdu.edu.cn/showproblem.php?pid=2647
View Code
 1 #include<iostream>
 2 #include<cstring>
 3 using namespace std ;
 4 #define M 10005
 5 struct node
 6 {
 7     int degree ;
 8     int v ;
 9     int money ;
10     node *next ;
11 }s[M] ;
12 int q[M*100], mark[M] ;
13 int find(int a, int b)
14 {
15     node *p = new node ;
16     for(p=s[a].next; p!=NULL; p=p->next)
17     if(p->v==b)
18     return 1 ;
19     return 0 ;
20 }
21 int add(int a, int b)
22 {
23     if(!find(a,b))
24     {
25         node *p = new node ;
26         p->next = s[a].next ;
27         p->v = b ;
28         s[a].next = p ;
29         s[b].degree++ ;
30     }
31     return 0 ;
32 }
33 int topological(int n)
34 {
35     int i, k, l, h, ans = 0, flag = 0 ;
36     l = h = 0 ;
37     for(i=1; i<=n; i++)
38     if(mark[i])
39     {
40         flag = 1 ;
41         if(s[i].degree==0)
42         q[l++] = i ;
43     }
44     if(flag&&l==0)
45     return -1 ;
46     node *p = new node ;
47     while(h<l)
48     {
49         k = q[h++] ;
50         ans += s[k].money ;
51         for(p=s[k].next; p!=NULL; p=p->next)
52         {
53             if(s[p->v].degree>0)
54             {
55                 s[p->v].degree-- ;
56                 s[p->v].money = s[k].money+1 ;
57                 if(s[p->v].degree==0)
58                 q[l++] = p->v ;
59             }
60         }
61 
62     }
63     for(i=1; i<=n; i++)
64     if(mark[i]&&s[i].degree)
65     return -1 ;
66     for(i=1; i<=n; i++)
67     if(!mark[i])
68     ans += 888 ;
69     return ans ;
70 }
71 int main()
72 {
73     int n, m, i, x, y ;
74     while(cin>>n>>m)
75     {
76         for(i=1; i<=n; i++)
77         {
78             s[i].next = NULL ;
79             s[i].degree = 0 ;
80             s[i].money = 888 ;
81             mark[i] = 0 ;
82         }
83         while(m--)
84         {
85             cin>>x>>y ;
86             add(y, x) ;
87             mark[x] = mark[y] = 1 ;
88 
89         }
90         int tosort = topological(n) ;
91         cout<<tosort<<endl ;
92     }
93     return 0 ;
94 }
多看几遍，好好理解