1 #include <iostream>  
 2 #include <algorithm>  
 3 #include <cstring>  
 4 #include <cstdio>  
 5 #include <vector>  
 6 #include <queue>  
 7 using namespace std;  
 8 const int maxn = 1e3 + 5;  
 9 struct node  
10 {  
11     int to, w;  
12     node(){}  
13     node(int tt, int ww) : to(tt), w(ww){}  
14 };  
15 vector<node> v[maxn];  
16 int e[maxn], deg[maxn], n, m, x, y, z;  
17 void TOP()  
18 {  
19     queue<int> q;  
20     for(int i = 0; i < n; i++)  
21         if(!deg[i])  
22             q.push(i), e[i] = 1;  
23     while(!q.empty())  
24     {  
25         int u = q.front();  
26         q.pop();  
27         for(int i = 0; i < v[u].size(); i++)  
28         {  
29             int to = v[u][i].to, w = v[u][i].w;  
30             if(e[to] < e[u]+w)  
31                 e[to] = e[u]+w;  
32             if(--deg[to] == 0)  
33                 q.push(to);  
34         }  
35     }  
36 }  
37 int main()  
38 {  
39     while(~scanf("%d%d", &n, &m))  
40     {  
41         memset(deg, 0, sizeof(deg));  
42         memset(e, 0, sizeof(e));  
43         for(int i = 0; i < maxn; i++)  
44             v[i].clear();  
45         for(int i = 1; i <= m; i++)  
46         {  
47             scanf("%d%d%d", &x, &y, &z);  
48             v[x].push_back(node(y, z));  
49             deg[y]++;  
50         }  
51         TOP();  
52         int ans = 0;  
53         for(int i = 0; i < n; i++)  
54             ans = max(ans, e[i]);  
55         printf("%d\n", ans);  
56     }  
57     return 0;  
58 }  

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<queue>
 5 using namespace std;
 6 struct edge{
 7     int to;
 8     int len;
 9     int next;
10 }qwq[11150];
11 queue<int>pa;
12 int edge_cnt,head[1005],stk[1005],dist[1005];
13 void add(int x,int y,int z)
14 {
15     qwq[edge_cnt].to=y;
16     qwq[edge_cnt].len=z;
17     qwq[edge_cnt].next=head[x];
18     head[x]=edge_cnt++;
19 }
20 void spfa()
21 {
22     while(!pa.empty())
23     {
24         pa.pop();
25     }
26     pa.push(0);
27     stk[0]=1;
28     while(!pa.empty())
29     {
30         int u=pa.front();pa.pop();stk[u]=0;
31         for(int i = head[u]; i != -1 ; i=qwq[i].next)
32         {
33             int v=qwq[i].to;
34             int llen=qwq[i].len;
35             if(dist[v]<llen+dist[u])
36             {
37                 dist[v]=llen+dist[u];
38                 if(!stk[v])
39                 {
40                     stk[v]=1;
41                     pa.push(v);
42                 }
43             }
44         }
45     }
46 }
47 int main()
48 {
49     int n,m;
50     while(scanf("%d%d",&n,&m)==2)
51     {
52         memset(head,-1,sizeof(head));
53         memset(dist,-1,sizeof(dist));
54         memset(stk,0,sizeof(stk));
55         dist[0]=0;
56         edge_cnt=0;
57         while(m--)
58         {
59             int a,b,c;
60             scanf("%d%d%d",&a,&b,&c);
61             add(a,b,c);
62         }
63         for(int i = 1 ; i <= n ;i++)
64         {
65             add(0,i,0);
66         }
67         spfa();
68         int maxx=-1;
69         for(int i = 0 ; i <= n ; i++)
70         {
71             if(dist[i]>maxx)
72             {
73                 maxx=dist[i];
74             }
75         }
76         cout << maxx+1 << endl;
77     }
78     return 0;
79 }