拓扑排序系列

　　关键路径：证明。好吧，我果然智商地下，照着模板码都搞这么久，代码又臭又长。。

  1 #include<cstdio>
  2 #include<cstring>
  3 #include<vector>
  4 #include<algorithm>
  5 #include<cstdlib>
  6 #include<queue>
  7 #include<stack>
  8 using namespace std;
  9 const int maxn = 1010;
 10 const int INF = 1<<29;
 11 int n,m;
 12 struct Edge{
 13     int from,to,dist;
 14     Edge(int from,int to,int dist):from(from),to(to),dist(dist){}
 15 };
 16 
 17 vector<Edge> edges;
 18 vector<int > G1[maxn];
 19 vector<int > G2[maxn];
 20 
 21 int fast[maxn];
 22 int last[maxn];
 23 int vend[maxn];
 24 int num_in[maxn];
 25 void init()
 26 {
 27     for(int i = 0;i <= n;i++) last[i] = INF;
 28     memset(fast,0,sizeof(fast));
 29 }
 30 
 31 void AddEdge(int from,int to,int dist)
 32 {
 33     edges.push_back(Edge(from,to,dist));
 34     edges.push_back(Edge(to,from,dist));
 35     int m = edges.size();
 36     G1[from].push_back(m-2);
 37     G2[to].push_back(m-1);  
 38 }
 39 
 40 
 41 void topsort()
 42 {
 43     queue<int> Q;
 44     stack<int> S;
 45     for(int i = 1;i <= n;i++)
 46         if(!num_in[i]) Q.push(i); 
 47     int vis[maxn];
 48     memset(vis,0,sizeof(vis));
 49     while(!Q.empty())
 50     {
 51         int u = Q.front();Q.pop();
 52         if(vis[u]) continue;
 53         vis[u] = 1;    
 54         S.push(u);
 55         for(int i = 0;i < G1[u].size();i++)
 56         {
 57             Edge& e = edges[G1[u][i]];
 58             num_in[e.to]--;
 59             fast[e.to] = max(fast[e.to],fast[e.from]+e.dist);
 60             if(!num_in[e.to])
 61                 Q.push(e.to); 
 62         }    
 63     }
 64     memset(vis,0,sizeof(vis));
 65     last[n] = fast[n];
 66     while(!S.empty())
 67     {    
 68         int u = S.top();S.pop();
 69         if(vis[u]) continue;
 70         vis[u] = 1;
 71         for(int i = 0;i < G2[u].size();i++)
 72         {
 73             Edge& e = edges[G2[u][i]];
 74             last[e.to] = min(last[e.to],last[e.from] - e.dist); 
 75         }
 76     }
 77     memset(vis,0,sizeof(vis));
 78     vector<int> ans;
 79     for(int i = 1;i <= n-1;i++)
 80     {
 81         for(int j = 0;j < G1[i].size();j++)
 82         {
 83             Edge& e = edges[G1[i][j]];
 84             vend[e.from] = last[e.to] - e.dist;
 85             if(vend[e.from] == fast[e.from])
 86                 ans.push_back(G1[i][j]/2+1);
 87         }
 88     }
 89     sort(ans.begin(),ans.end());
 90     for(int i = 0;i < ans.size();i++)
 91         printf("%d\n",ans[i]);
 92 }
 93 int main()
 94 {
 95     scanf("%d%d",&n,&m);
 96     init();
 97     for(int i =0 ;i < m;i++)
 98     {
 99         int from,to,dist;
100         scanf("%d%d%d",&from,&to,&dist);
101         num_in[to]++;
102         AddEdge(from,to,dist);        
103     }
104     topsort();    
105     return 0;
106 }
关键路径

　　呃呃呃，既然是拓扑排序系列，我就不写拓扑排序了23333

posted @ 2017-03-10 21:23  rsqppp  阅读(106)  评论(0)    收藏  举报