hdu2544 （SPFA)

题意：单源最短路
解题思路：队列优化的 bellman-ford 算法！
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 #include<queue>
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 queue <int> lis;
42 int bellman_ford(int s)
43 {
44     for(int i = 1;i <= n;i ++) dis[i] = 1 << 27; 
45     dis[s] = 0 ; 
46     lis.push(s);
47     while(!lis.empty())
48     {
49         int k = lis.front();
50         lis.pop();
51         int n = edge[k].size();
52         for(int i = 0 ;i < n ;i ++)
53         {
54            if(dis[edge[k][i].x] > dis[k] + edge[k][i].d)
55            {
56                dis[edge[k][i].x] = dis[k] + edge[k][i].d;
57                lis.push(edge[k][i].x);
58            }
59         }
60     }
61     return 1;   
62 }
63 int main(){
64     //freopen("/home/plac/problem/input.txt","r",stdin);
65     //freopen("/home/plac/problem/output.txt","w",stdout);
66     while(scanf("%d %d",&n,&m)!= EOF)
67     {
68         if(n == 0 && m == 0 )
69             break;
70         for(int i =1 ;i <= n;i++)
71             edge[i].clear();
72         for(int i = 1;i <= m ;i ++)
73         { 
74             int a, b, c;
75             scanf("%d %d %d",&a,&b,&c);
76             edge[a].push_back(node(b,c));
77             edge[b].push_back(node(a,c));
78         }
79         if(bellman_ford(1))
80             printf("%d\n",dis[n]);
81     }
82     return 0;
83 }
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posted on 2014-04-05 08:08 dark_dream 阅读(168) 评论(0) 编辑收藏举报