POJ 2387 Til the Cows Come Home

Posted 2020-11-17 ducklu

思路:Dijkstra, bellman-ford和spfa，但是用dijkstra要考虑重边

 1 #include <iostream>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <stack>
 5 #include <cstdio>
 6 #include <queue>
 7 #define MAXVERTEXNUM 1010
 8 #define INF 99999999
 9 #define ERROR -1
10 using namespace std;
11 
12 int MGraph[MAXVERTEXNUM][MAXVERTEXNUM];
13 int dist[MAXVERTEXNUM];
14 int Nv, Ne;
15 int collected[MAXVERTEXNUM];
16 
17 int FindMinDist()
18 {
19     int MinDist = INF;
20     int MinV;
21     for (int i = 1; i < Nv; ++i)
22     {
23         if (!collected[i] && dist[i] < MinDist)
24         {
25             MinDist = dist[i];
26             MinV = i;
27         }
28     }
29     if (MinDist != INF)
30         return MinV;
31     return ERROR;
32 }
33 
34 void Dijkstra()
35 {
36     memset(collected, 0, sizeof(collected));
37 
38     int start = Nv;
39     //init start
40     dist[start] = 0;
41     collected[start] = 1;
42     for (int i = 1; i < Nv; ++i)//start did not need to involve
43     {
44         dist[i] = MGraph[i][start];
45     }
46 
47     while (true)
48     {
49         int V = FindMinDist();
50         if (V == ERROR)
51             break;
52         collected[V] = 1;
53         for (int i = 1; i < Nv; ++i)
54         {
55             if (!collected[i] && dist[V] + MGraph[V][i] < dist[i])//&& MGraph[V][i] != INF
56                     dist[i] = dist[V] + MGraph[V][i];
57         }
58     }
59 }
60 
61 int main()
62 {
63     ios::sync_with_stdio(false);
64     cin >> Ne >> Nv;
65 
66     //init
67     for (int i = 1; i <= Nv; ++i)
68     {
69         for (int j = 1; j <= Nv; ++j)
70         {
71             MGraph[i][j] = INF;
72         }
73     }
74 
75 
76     for (int i = 0; i < Ne; ++i)
77     {
78         int V1, V2, E;
79         cin >> V1 >> V2 >> E;
80         if (MGraph[V1][V2] > E)
81         {
82             MGraph[V1][V2] = E;
83             MGraph[V2][V1] = E;
84         }
85     }
86 
87     Dijkstra();
88     cout << dist[1] << endl;
89 
90     return 0;
91 }