UVA 11280 Flying to Fredericton

用spfa做的时候 标记每个点的被松弛的次数 即可。

View Code 
  1 #include <iostream>
  2 #include <vector>
  3 #include <cstring>
  4 #include <queue>
  5 #include <string>
  6 #include <map>
  7 #include <cstdio>
  8 #define maxn 110
  9 #define INF 1 << 30
 10 using namespace std;
 11 typedef pair<int,int> pii;
 12 vector<int> v,next,w;
 13 int first[maxn],e;
 14 int inq[maxn][maxn],d[maxn][maxn];
 15 
 16 inline int min(int a,int b)
 17 {
 18     return a < b ? a : b;
 19 }
 20 
 21 void init()
 22 {
 23     v.clear();
 24     next.clear();
 25     w.clear();
 26     memset(first,-1,sizeof(first));
 27     e = 0;
 28 }
 29 
 30 void add_edge(int a,int b,int c)
 31 {
 32     v.push_back(b);
 33     next.push_back(first[a]);
 34     first[a] = e;
 35     w.push_back(c);
 36     e++;
 37 }
 38 
 39 void spfa(int start,int end,int n,int len)
 40 {
 41     if(len > maxn - 1)  len = maxn - 1;//这里太淫荡了。。
 42     queue <pii> q;
 43     for(int i = 0;i <= len;i++)
 44         for(int j = 0;j <= n;j++)
 45         {
 46             inq[i][j] = 0;
 47             d[i][j] = INF;
 48         }
 49 
 50     d[0][start] = 0;
 51     inq[0][start] = 1;
 52     q.push(make_pair(0,start));
 53 
 54     while(!q.empty())
 55     {
 56         int times = q.front().first;
 57         int u = q.front().second;
 58         //printf("current times = %d,current point = %d\n",times,u);
 59         inq[times][u] = 0;
 60         q.pop();
 61 
 62         for(int i = first[u];i != -1;i = next[i])
 63         {
 64             if(times + 1 <= len && d[times + 1][v[i]] > d[times][u] + w[i])
 65             {
 66                 //printf("succeed:times = %d,point = %d,dist = %d\n",times,v[i],d[times][u] + w[i]);
 67                 d[times + 1][v[i]] = d[times][u] + w[i];
 68                 if(!inq[times + 1][v[i]])
 69                 {
 70                     inq[times + 1][v[i]] = 1;
 71                     q.push(make_pair(times + 1,v[i]));
 72                 }
 73             }
 74         }
 75     }
 76 
 77     int ans = INF;
 78     for(int t = 0;t <= len;t++)
 79         ans = ans < d[t][end] ? ans : d[t][end];
 80 
 81     if(ans == INF)  printf("No satisfactory flights\n");
 82     else            printf("Total cost of flight(s) is $%d\n",ans);
 83 }
 84 
 85 int main()
 86 {
 87     int T;
 88     scanf("%d",&T);
 89     for(int kase = 1;kase <= T;kase++)
 90     {
 91         map<string,int> m;
 92         int start,end;
 93         int n,M;
 94         scanf("%d",&n);
 95         for(int i = 0;i < n;i++)
 96         {
 97             string str;
 98             cin>>str;
 99             m[str] = i;
100             if(str == "Calgary")    start = i;
101             else if(str == "Fredericton")    end = i;
102         }
103         //printf("start = %d,end = %d\n",start,end);
104         init();
105         scanf("%d",&M);
106         for(int i = 0;i < M;i++)
107         {
108             int cost;
109             string str1,str2;
110             cin>>str1>>str2>>cost;
111             add_edge(m[str1],m[str2],cost);
112         }
113 
114         if(kase > 1)    printf("\n");
115         printf("Scenario #%d\n",kase);
116         int q,len;
117         scanf("%d",&q);
118         while(q--)
119         {
120             scanf("%d",&len);
121             spfa(start,end,n,len + 1);
122         }
123 
124     }
125     return 0;
126 }

 

posted @ 2013-03-03 12:30  浙西贫农  阅读(377)  评论(0)  编辑  收藏  举报