uva oj 567 - Risk(Floyd算法)

 1 /*
 2 一张有20个顶点的图上。
 3 依次输入每个点与哪些点直接相连。
 4 并且多次询问两点间，最短需要经过几条路才能从一点到达另一点。
 5 
 6 bfs 水过
 7 */
 8 #include<iostream>
 9 #include<cstring>
10 #include<vector>
11 #include<cstdio>
12 #include<queue>
13 using namespace std;
14 
15 struct node{
16    int x, step;
17    node(){
18    
19    }
20    node(int x, int step){
21       this->x=x;
22       this->step=step;
23    }
24 }; 
25 
26 
27 vector<int>v[25]; 
28 queue<node>q;
29 int vis[25];
30 
31 
32 int b, e;
33 
34 void bfs(){
35    while(!q.empty())  q.pop();
36    node cur;
37    q.push(node(b, 0));
38    while(!q.empty()){
39        cur=q.front();
40        q.pop();
41        if(cur.x==e){
42            printf("%2d to %2d: %d\n", b, e, cur.step);
43            return;
44        }
45        int len=v[cur.x].size();
46        for(int i=0; i<len; ++i){
47              if(v[cur.x][i]==e){
48              printf("%2d to %2d: %d\n", b, e, cur.step+1);
49              return;
50           }
51           if(!vis[v[cur.x][i]]){
52                vis[v[cur.x][i]]=1;
53              q.push(node(v[cur.x][i], cur.step+1));
54           } 
55        }
56    }
57 }
58 
59 int main(){
60     int n, u;
61     int cnt=0;
62     while(scanf("%d", &n)!=EOF){
63         while(n--){
64            scanf("%d", &u);
65            v[1].push_back(u);
66            v[u].push_back(1);
67         }
68         for(int i=2; i<=19; ++i){
69            scanf("%d", &n);
70            while(n--){
71               scanf("%d", &u);
72               v[i].push_back(u);
73               v[u].push_back(i);
74            }
75         }
76         scanf("%d", &n);
77         printf("Test Set #%d\n", ++cnt);
78         while(n--){
79            scanf("%d%d", &b, &e) ;
80            bfs();
81            memset(vis, 0, sizeof(vis));
82         }
83         printf("\n");
84         for(int i=1; i<=20; ++i)
85            v[i].clear();
86            
87     } 
88     return 0;
89 }

 1 /*
 2    Floyd 才是正解！
 3 */
 4 #include<iostream>
 5 #include<cstring>
 6 #include<vector>
 7 #include<cstdio>
 8 #include<queue>
 9 #define INF 0x3f3f3f3f
10 using namespace std;
11 
12 int map[25][25];
13 
14 void Folyd(){
15    for(int k=1; k<=20; ++k)
16       for(int i=1; i<=20; ++i)
17          for(int j=1; j<=20; ++j)
18             if(map[i][j] > map[i][k] + map[k][j])
19                map[i][j] = map[i][k] + map[k][j];
20 }
21 
22 
23 int main(){
24     int n, u, b, e;
25     int cnt=0;
26     while(scanf("%d", &n)!=EOF){
27         memset(map, 0x3f, sizeof(map));
28         while(n--){
29            scanf("%d", &u);
30            map[1][u]=map[u][1]=1;
31         }
32         for(int i=2; i<=19; ++i){
33            scanf("%d", &n);
34            while(n--){
35               scanf("%d", &u);
36               map[u][i]=map[i][u]=1;
37            }
38         }
39         scanf("%d", &n);
40         printf("Test Set #%d\n", ++cnt);
41         Folyd();
42         while(n--){
43            scanf("%d%d", &b, &e) ;
44            printf("%2d to %2d: %d\n", b, e, map[b][e]);
45         }
46         printf("\n");
47     }
48 }