【板子】最小生成树

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 const int maxn=1001;
 5 using namespace std;
 6 
 7 int c,n,m;
 8 int map[maxn][maxn];
 9 int dis[maxn];
10 bool vis[maxn];
11 
12 int prim(){
13     memset(dis,0x3f,sizeof(dis));
14     memset(vis,0,sizeof(vis)); 
15     int ans=0;
16     dis[1]=0;
17     while(1){
18         int k=0;
19         for(int j=1;j<=n;j++){
20             if(!vis[j]&&dis[j]<dis[k])
21                 k=j; 
22         } 
23         if(!k) break;
24         vis[k]=1; 
25         ans+=dis[k];
26         for(int j=1;j<=n;j++){
27             if(dis[j]>map[k][j]){
28                 dis[j]=map[k][j];
29             }
30 
31         }
32     }
33     return ans;
34 }
35 int main(){
36 
37     while(cin>>c>>m>>n){
38         int x,y,z;
39         memset(map,0x3f,sizeof(map));  
40         for(int i = 0; i < m; i++){
41             cin>>x>>y>>z;
42             map[x][y]=map[y][x]=min(map[x][y],z);
43         }
44         int ans = prim();
45       //  cout<<ans<<endl;
46         if(ans > c || ans == 0){
47             cout<<"No"<<endl;
48         }
49         else{
50             cout<<"Yes"<<endl;
51         }
52     }
53     return 0;
54 }

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<string.h>
 4 #include<algorithm>
 5 #include<fstream>
 6 using namespace std;
 7  
 8 const int MAXN=505;//最大点数
 9 const int MAXM=250005;//最大边数
10 int f[MAXN];
11  
12 struct Edge{
13     int u,v,w;
14 }edge[MAXM];
15  
16 int cnt;
17  
18 
19 bool cmp(Edge a,Edge b){
20     return a.w<b.w;
21 }
22  
23 int find(int x){
24     if(f[x] == -1)
25         return x;
26     else
27         return f[x] = find(f[x]);
28 }
29 
30 int Kruskal(int n){
31     memset(F,-1,sizeof(F));
32     sort(edge,edge+cnt,cmp);
33     int cnt1 = 0;//计算加入的边数
34     int ans = 0;
35     for(int i = 0; i < cnt;i++){
36         int u = edge[i].u;
37         int v = edge[i].v;
38         int w = edge[i].w;
39         int t1 = find(u);
40         int t2 = find(v);
41         if(t1 != t2){
42             ans += w;
43             f[t1] = t2;
44             cnt1++;
45         }
46         if(cnt1 == n-1)
47             break;
48     }
49     if(cnt1 < n-1)
50         return -1;//不连通
51     else
52         return ans;
53 }
54  
55 int main(){
56     int c,n,m;
57     cin>>c>>m>>n;
58     cnt=0;
59     for(int i = 1; i <= m ;i++){
60         int x,y,z;
61         cin>>x>>y>>z;
62         edge[cnt].u = x;
63         edge[cnt].v = y;
64         edge[cnt++].w = z;
65     }
66     int ans = Kruskal(n);
67    
68     if(ans > c || ans == -1){
69         cout<<"No"<<endl;
70     }
71     else{
72         cout<<"Yes"<<endl;
73     }
74     
75     return 0;
76 }