CF 1005F Berland and the Shortest Paths

Posted 2021-01-16 lnxcj

最短路树

 1 #include<queue>
 2 #include<vector>
 3 #include<cstdio>
 4 #include<cstring>
 5 #include<algorithm>
 6 using namespace std;
 7 int n,m,cnt,tot,num,k;
 8 vector<int>cty[200005];
 9 int head[200005];
10 int fa[200005];
11 int dis[200005];
12 int usd[200005];
13 struct Edge{
14     int fr;
15     int to;
16     int id;
17     int nxt;
18 }edge[400005];
19 void init(){
20     tot=1;
21     memset(dis,0x3f,sizeof(dis));
22     memset(head,-1,sizeof(head));
23 }
24 void addedge(int f,int t,int x){
25     cnt++;
26     edge[cnt].fr=f;
27     edge[cnt].to=t;
28     edge[cnt].id=x;
29     edge[cnt].nxt=head[f];
30     head[f]=cnt;
31 }
32 void bfs(){
33     dis[1]=0;
34     queue<int>que;
35     que.push(1);
36     while(!que.empty()){
37         int s=que.front();
38         que.pop();
39         for(int i=head[s];i!=-1;i=edge[i].nxt){
40             int v=edge[i].to;
41             if(dis[v]>dis[s]+1){
42                 dis[v]=dis[s]+1;
43                 cty[v].push_back(edge[i].id);
44                 que.push(v);
45             }
46             else if(dis[v]==dis[s]+1){
47                 cty[v].push_back(edge[i].id);
48             }
49         }
50     }
51 }
52 void dfs(int dep){
53     if(dep==n+1){
54         for(int i=1;i<=m;i++){
55             printf("%d",usd[i]);
56         }
57         printf("
");
58         num++;
59         if(num==tot){
60             exit(0);
61         }
62         return;
63     }
64     for(int i=0;i<cty[dep].size();i++){
65         usd[cty[dep][i]]=1;
66         dfs(dep+1);
67         usd[cty[dep][i]]=0;
68     }
69 }
70 int main(){
71     init();
72     scanf("%d%d%d",&n,&m,&k);
73     for(int i=1;i<=m;i++){
74         int u,v;
75         scanf("%d%d",&u,&v);
76         addedge(u,v,i);
77         addedge(v,u,i);
78     }
79     bfs();
80     for(int i=2;i<=n;i++){
81         tot*=cty[i].size();
82         if(tot>=k){
83             tot=k;
84             break;
85         }
86     }
87     printf("%d
",tot);
88     dfs(2);
89     return 0;
90 }