HDU 1827 Summer Holiday

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<cstring>
 4 #include<cstdio>
 5 #include<vector>
 6 #include<queue>
 7 #include<cmath>
 8 #include<map>
 9 #include<stack>
10 using namespace std;
11 
12 const int INF=0x3f3f3f;
13 const int maxn=1000+5;
14 int n,m;
15 
16 vector<int> G[maxn];
17 int pre[maxn],lowlink[maxn],sccno[maxn],dfs_clock,scc_cnt;
18 int scc_v[maxn];
19 stack<int> S;
20 int a[maxn];
21 int in[maxn];
22 
23 void dfs(int u) {
24     pre[u] = lowlink[u] = ++dfs_clock;
25     S.push(u);
26     for (int i = 0; i < G[u].size(); i++)
27     {
28         int v = G[u][i];
29         if (!pre[v])
30         {
31             dfs(v);
32             lowlink[u] = min(lowlink[u], lowlink[v]);
33         }
34         else if(!sccno[v])
35         lowlink[u] = min(lowlink[u], pre[v]);
36     }
37     if (pre[u] == lowlink[u])
38     {
39         scc_cnt++;
40         scc_v[scc_cnt] = INF;
41         for(;;)
42         {
43             int x = S.top(); S.pop();
44             //计算出每个连通分支中的最小权值
45             scc_v[scc_cnt] = min(scc_v[scc_cnt], a[x]);
46             sccno[x] = scc_cnt;
47             if (x == u) break;
48         }
49     }
50 }
51 
52 void find_scc(int n)
53 {
54     dfs_clock = scc_cnt = 0;
55     memset(pre, 0, sizeof(pre));
56     memset(sccno, 0, sizeof(sccno));
57     for (int i = 1; i <= n; i++)
58         if (!pre[i]) dfs(i);
59 }
60 
61 
62 int main()
63 {
64     //freopen("D:\\input.txt","r",stdin);
65     while(scanf("%d%d",&n,&m)==2)
66     {
67         for(int i=1;i<=n;i++)   G[i].clear();
68         for(int i=1;i<=n;i++)   scanf("%d",&a[i]);
69         while(m--)
70         {
71             int u,v;
72             scanf("%d%d",&u,&v);
73             G[u].push_back(v);
74         }
75         find_scc(n);
76         memset(in,0,sizeof(in));
77         for(int u=1;u<=n;u++)
78         {
79             for(int i=0;i<G[u].size();i++)
80             {
81                 int v=G[u][i];
82                 if(sccno[u]!=sccno[v])  in[sccno[v]]=1;
83             }
84         }
85         int ans=0,num=0;
86         for(int i=1;i<=scc_cnt;i++)
87         {
88             if(in[i]==0)
89             {
90                 ans+=scc_v[i];
91                 num++;
92             }
93         }
94         printf("%d %d\n",num,ans);
95     }
96     return 0;
97 }