dijkstra算法

 1 #include <iostream>
 2 #include <vector>
 3 #include <cstring>
 4 #include <fstream>
 5 #include <algorithm>
 6 using namespace std;
 7 const int INF=99999999;
 8 int grap[1005][1005];
 9 int dist[1005];
10 bool used[1005];
11 int T,N;
12 
13 void init()
14 {
15     for(int i=1; i<=N; i++)
16         for(int j=1; j<=N; j++)
17         {
18             if(i==j)
19                 grap[i][j]=0;
20             else
21                 grap[i][j]=INF;
22         }
23 }
24 
25 int dijkstra()
26 {
27     fill(used,used + 1005,false);
28     for(int i=1; i<=N; i++)
29         dist[i] = INF;
30     dist[1] = 0;
31 
32     for(int i = 2; i <= N; i++)
33     {
34         dist[i] = grap[1][i];
35     }
36 
37     for(int i = 1; i <= N; i++)
38     {
39         int min_c = INF,x;
40         for(int j = 1; j <= N; j++)
41         {
42             if(!used[j] && dist[j] < min_c)
43             {
44                 min_c = dist[j];
45                 x = j;
46             }
47         }
48         used[x] = true;
49         for(int u = 1; u <= N; u++)
50         {
51             dist[u] = min(dist[u] , (dist[x] + grap[x][u]) );
52         }
53     }
54 
55     return dist[N];
56 }
57 
58 int main()
59 {
60     //freopen("in.txt","r",stdin);
61     while (cin >> T >> N)
62     {
63         init();
64 
65         for(int i = 0; i < T; i++)
66         {
67             int s,t,c;
68             cin >> s >> t >> c;
69             grap[t][s] = grap[s][t] = min(grap[s][t],c);
70         }
71 
72         cout<<dijkstra()<<endl;
73     }
74 
75 
76     return 0;
77 }

 1 #include <iostream>
 2 #include <vector>
 3 #include <cstring>
 4 #include <queue>
 5 #include <fstream>
 6 #include <algorithm>
 7 using namespace std;
 8 int T, N;
 9 const int INF=99999999;
10 int cnt;
11 int lastshow[40010];
12 int dist[40010];
13 bool used[40010];
14 typedef pair<int, int> P;
15 priority_queue<P, vector<P>, greater<P> > q;
16 
17 
18 struct edge{
19     int to;
20     int wei;
21     int next;
22 }grap[40010];
23 
24 void insert(int a, int b, int c){
25     cnt ++;
26     grap[cnt].to = b;
27     grap[cnt].next = lastshow[a];
28     grap[cnt].wei = c;
29     lastshow[a] = cnt;
30 }
31 
32 
33 void dijkstra(){
34     memset(used, 0, sizeof(used));
35     q.push(make_pair(dist[1], 1));
36     while(!q.empty()){
37         P u = q.top();
38         q.pop();
39         int x = u.second;
40         if(used[x])
41             continue;
42         used[x] = true;
43         for(int i = lastshow[x]; i != -1; i = grap[i].next){
44             if(dist[grap[i].to] > dist[x] + grap[i].wei){
45                 dist[grap[i].to] = dist[x] + grap[i].wei;
46                 q.push(make_pair(dist[grap[i].to], grap[i].to));
47             }
48         }
49     }
50 }
51 
52 
53 
54 int main()
55 {
56     //freopen("in.txt","r",stdin);
57     while (cin >> T >> N)
58     {
59         cnt = 0;
60         memset(lastshow, -1, sizeof(lastshow));
61         for(int i = 1; i <= N; i ++)
62             dist[i] = (i == 1 ? 0 : INF);
63         for(int i = 0; i < T; i ++)
64         {
65             int a, b, c;
66             cin >> a >> b >> c;
67             insert(a, b, c);
68             insert(b, a, c);
69         }
70 
71         dijkstra();
72         cout<<dist[N]<<endl;
73     }
74 
75 
76     return 0;
77 }