hdu2544 （bellman-ford)

题意：求顶点 1 - 顶点n 之间的最短路

解题思路：bellman-ford 算法，利用n-1松弛操作得到最短路，算法复杂度为 V*E

解题代码：

 1 // File Name: 2544_1.cpp
 2 // Author: darkdream
 3 // Created Time: 2014年04月04日 星期五 22时37分45秒
 4 
 5 #include<vector>
 6 #include<list>
 7 #include<map>
 8 #include<set>
 9 #include<deque>
10 #include<stack>
11 #include<bitset>
12 #include<algorithm>
13 #include<functional>
14 #include<numeric>
15 #include<utility>
16 #include<sstream>
17 #include<iostream>
18 #include<iomanip>
19 #include<cstdio>
20 #include<cmath>
21 #include<cstdlib>
22 #include<cstring>
23 #include<ctime>
24 #include<climits>
25 
26 using namespace std;
27 
28 struct node{
29     int x, d ; 
30     node()
31     {}
32     node(int p,int q)
33     {
34         x = p; 
35         d = q; 
36     }
37 };
38 vector <node> edge[200];
39 int n , m ; 
40 int dis[200];
41 int bellman_ford(int s)
42 {
43     for(int i = 1;i <= n;i ++) dis[i] = 1 << 27; 
44     dis[s] = 0 ; 
45     for(int i = 1;i <= n -1;i ++)
46     {
47         for(int j = 1;j <= n;j ++)
48         {
49             int k = edge[j].size();
50             for(int p = 0 ;p < k ;p ++)
51             {
52                 if(dis[edge[j][p].x] > dis[j] + edge[j][p].d)
53                     dis[edge[j][p].x] = dis[j] + edge[j][p].d; 
54             }
55         }
56     }
57     return 1;   
58 }
59 int main(){
60     //freopen("/home/plac/problem/input.txt","r",stdin);
61     //freopen("/home/plac/problem/output.txt","w",stdout);
62     while(scanf("%d %d",&n,&m)!= EOF)
63     {
64         if(n == 0 && m == 0 )
65             break;
66         for(int i =1 ;i <= n;i++)
67             edge[i].clear();
68         for(int i = 1;i <= m ;i ++)
69         { 
70             int a, b, c;
71             scanf("%d %d %d",&a,&b,&c);
72             edge[a].push_back(node(b,c));
73             edge[b].push_back(node(a,c));
74         }
75         if(bellman_ford(1))
76             printf("%d\n",dis[n]);
77     }
78     return 0;
79 }

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posted on 2014-04-04 23:09 dark_dream 阅读(169) 评论(0) 编辑收藏举报