1 #include <stdlib.h>
2 #include <cstdio>
3 #include <queue>
4 #define MaxVertexNum 102
5 #define INFINITY 65536
6 using namespace std;
7
8 typedef int Vertex;
9 typedef int WeightType;
10 typedef int DataType;
11
12 int Indegree[MaxVertexNum];
13
14
15 typedef struct ENode *Edge;
16 struct ENode{
17 Vertex V1, V2;
18 WeightType Weight;
19 };
20
21 typedef struct AdjVNode *PtrToAdjVNode;
22 struct AdjVNode{
23 Vertex AdjV;
24 WeightType Weight;
25 PtrToAdjVNode Next;
26 };
27
28 typedef struct Vnode{
29 PtrToAdjVNode FirstEdge;
30 DataType Data;
31 } AdjList[MaxVertexNum]; /* AdjListÊÇÁÚ½Ó±íÀàÐÍ */
32
33
34
35 typedef struct GNode *LGraph;
36 struct GNode{
37 int Nv;
38 int Ne;
39 AdjList G;
40 };
41
42
43
44 LGraph CreateGraph( int VertexNum );
45 void InsertEdge( LGraph Graph, Edge E );
46 LGraph BuildGraph();
47 bool topSort(LGraph Graph);
48
49 void find_max(LGraph Graph);
50
51 int main() {
52 LGraph Graph = BuildGraph();
53
54 if( !topSort(Graph) ) printf("Impossible\n");
55 else {
56 find_max(Graph);
57 }
58
59
60 }
61
62 LGraph CreateGraph( int VertexNum )
63 {
64 Vertex V;
65 LGraph Graph;
66
67 Graph = (LGraph)malloc( sizeof(struct GNode) );
68 Graph->Nv = VertexNum;
69 Graph->Ne = 0;
70
71 for (V=0; V<Graph->Nv; V++)
72 Graph->G[V].FirstEdge = NULL;
73
74 return Graph;
75 }
76 void InsertEdge( LGraph Graph, Edge E )
77 {
78 PtrToAdjVNode newNode = new AdjVNode;
79 newNode->Weight = E->Weight;
80 newNode->AdjV = E->V2;
81
82 newNode->Next = Graph->G[E->V1].FirstEdge;
83 Graph->G[E->V1].FirstEdge = newNode;
84
85
86 }
87 LGraph BuildGraph()
88 {
89 LGraph Graph;
90 int Nv;
91 Edge E;
92 Vertex V;
93
94 scanf("%d", &Nv);
95 Graph = CreateGraph(Nv);
96
97 scanf("%d", &(Graph->Ne));
98
99 if(Graph->Ne) {
100 E = new ENode;
101 for(int i=0; i<Graph->Ne; i++) {
102 scanf("%d %d %d", &(E->V1), &(E->V2), &(E->Weight));
103 InsertEdge(Graph, E);
104 }
105 }
106
107 for(V=0; V<Graph->Nv; V++) {
108 Graph->G[V].Data = 0;
109 }
110 return Graph;
111
112 }
113 bool topSort(LGraph Graph)
114 {
115 int cnt;
116 Vertex V;
117 queue<Vertex> Q;
118
119 cnt = 0;
120 for( V=0; V<Graph->Nv; V++) Indegree[V] = 0;
121
122 for( V = 0; V < Graph->Nv; V++) {
123 for(PtrToAdjVNode W = Graph->G[V].FirstEdge; W; W=W->Next) {
124 Indegree[W->AdjV]++;
125 Graph->G[W->AdjV].Data = 0;
126 }
127 }
128 for(V=0; V<Graph->Nv; V++) if(Indegree[V] == 0) Q.push(V);
129
130 while(!Q.empty()) {
131 V = Q.front();
132 Q.pop();
133 cnt++;
134
135 for(PtrToAdjVNode W = Graph->G[V].FirstEdge; W; W=W->Next) {
136 if(--Indegree[W->AdjV] == 0) Q.push(W->AdjV);
137 if(Graph->G[W->AdjV].Data < W->Weight + Graph->G[V].Data)
138 Graph->G[W->AdjV].Data = W->Weight + Graph->G[V].Data;
139
140 }
141
142
143 }
144
145 if(cnt != Graph->Nv) return false;
146 return true;
147
148
149 }
150
151 void find_max(LGraph Graph)
152 {
153 Vertex V;
154 int compTime;
155 compTime = Graph->G[0].Data;
156
157 for(V = 1; V < Graph->Nv; V++) {
158 if(Graph->G[V].Data > compTime) compTime = Graph->G[V].Data;
159 }
160 printf("%d\n", compTime);
161 }
