hihoCoder #1175 : 拓扑排序·二

题目链接：http://hihocoder.com/problemset/problem/1175

代码实现如下：

 1 #include <queue>
 2 #include <cstdio>
 3 #include <cstring>
 4 using namespace std;
 5 
 6 const int maxn = 1e5 + 7;
 7 const int mod = 142857;
 8 int n, m, k, u, v, x;
 9 int InDeg[maxn], virus[maxn];
10 vector<int> G[maxn];
11 
12 void topsort() {
13     queue<int> q;
14     for(int i = 1; i <= n; i++) {
15         if(InDeg[i] == 0) {
16             q.push(i);
17         }
18     }
19     int x;
20     while(!q.empty()) {
21         x = q.front(), q.pop();
22         int s = G[x].size();
23         for(int i = 0; i < s; i++) {
24             if(--InDeg[G[x][i]] == 0) {
25                 q.push(G[x][i]);
26             }
27             virus[G[x][i]] = (virus[G[x][i]] + virus[x]) % mod;
28         }
29     }
30 }
31 
32 int main() {
33     while(~scanf("%d%d%d", &n, &m, &k)) {
34         for(int i = 0; i <= n; i++) {
35             G[i].clear();
36         }
37         memset(InDeg, 0, sizeof(InDeg));
38         memset(virus, 0, sizeof(virus));
39         for(int i = 0; i < k; i++) {
40             scanf("%d", &x);
41             virus[x] = 1;
42         }
43         for(int i = 0 ; i < m; i++) {
44             scanf("%d%d", &u, &v);
45             G[u].push_back(v);
46             InDeg[v]++;
47         }
48         topsort();
49         int ans = 0;
50         for(int i = 1; i <= n; i++) {
51             ans = (ans + virus[i]) % mod;
52         }
53         printf("%d\n", ans);
54     }
55     return 0;
56 }

 

posted @ 2018-05-07 17:52  Dillonh  阅读(159)  评论(0)  编辑  收藏  举报