POJ 1860 Currency Exchange(SPFA)

题目链接

SPFA果真是功能强大，1Y。

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <cmath>
 4 #include <queue>
 5 #include <iostream>
 6 using namespace std;
 7 #define N 10000000
 8 double p1[101][101],p2[101][101],d[101],v;
 9 int n;
10 int spfa(int str)
11 {
12     int in[101],u,i;
13     memset(in,0,sizeof(in));
14     for(i = 1;i <= n;i ++)
15     {
16         d[i] = 0;
17     }
18     d[str] = v;
19     queue<int> que;
20     que.push(str);
21     in[str] = 1;
22     while(!que.empty())
23     {
24         u = que.front();
25         in[u] = 0;
26         que.pop();
27         for(i = 1;i <= n;i ++)
28         {
29             if(p1[u][i] != N&&d[i] < (d[u]-p2[u][i])*p1[u][i])
30             {
31                 d[i] = (d[u]-p2[u][i])*p1[u][i];
32                 if(!in[i])
33                 {
34                     in[i] = 1;
35                     que.push(i);
36                 }
37             }
38         }
39         if(d[str] > v)
40         return 1;
41     }
42     return 0;
43 }
44 int main()
45 {
46     int m,str,sv,ev,i,j;
47     double w1,w2,w3,w4;
48     scanf("%d%d%d%lf",&n,&m,&str,&v);
49     for(i = 1;i <= n;i ++)
50     {
51         for(j = 1;j <= n;j ++)
52         {
53             p1[i][j] = N;
54             p2[i][j] = N;
55         }
56     }
57     for(i = 1;i <= m;i ++)
58     {
59         scanf("%d%d%lf%lf%lf%lf",&sv,&ev,&w1,&w2,&w3,&w4);
60         p1[sv][ev] = w1;
61         p2[sv][ev] = w2;
62         p1[ev][sv] = w3;
63         p2[ev][sv] = w4;
64     }
65     if(spfa(str))printf("YES\n");
66     else printf("NO\n");
67 }
posted @ 2012-11-27 19:23  Naix_x  阅读(192)  评论(0)    收藏  举报