题目链接:
http://acm.hdu.edu.cn/showproblem.php?pid=1863
题意:
题解:
Kruskal是按照边权排序，每次选择一条最小的边，判断这条边的两个端点是否在同一个集合，用并查集维护
Prim是随便选择一个点作为当前集合，找到与这个集合相连的边中最短的那条，用优先队列取出最短的，如果另一个端点不在当前集合，就加进来，并且把与这个点相连的所有边加到优先队列里
代码:
Kruskal：
1 #include <bits/stdc++.h> 2 using namespace std; 3 typedef long long ll; 4 #define MS(a) memset(a,0,sizeof(a)) 5 #define MP make_pair 6 #define PB push_back 7 const int INF = 0x3f3f3f3f; 8 const ll INFLL = 0x3f3f3f3f3f3f3f3fLL; 9 inline ll read(){ 10 ll x=0,f=1;char ch=getchar(); 11 while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} 12 while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();} 13 return x*f; 14 } 15 ////////////////////////////////////////////////////////////////////////// 16 const int maxn = 100+10; 17 18 int N,M,fa[maxn]; 19 ll ans; 20 21 struct node{ 22 int u,v,w; 23 bool operator<(const node& rhs)const{ 24 return w < rhs.w; 25 } 26 }E[maxn]; 27 28 int find(int x){ 29 return fa[x]==x ? x : fa[x]=find(fa[x]); 30 } 31 32 void Union(int x,int y){ 33 int p1 = find(x), p2 = find(y); 34 if(p1 == p2) return; 35 fa[p1] = p2; 36 } 37 38 bool same(int x,int y){ 39 return find(x)==find(y); 40 } 41 42 void kruskal(){ 43 sort(E,E+M); 44 for(int i=0; i<M; i++){ 45 int u = E[i].u, v = E[i].v, w = E[i].w; 46 if(same(u,v)) continue; 47 Union(u,v); 48 ans += w; 49 } 50 } 51 52 int main(){ 53 while(scanf("%d%d",&M,&N)==2){ 54 if(M==0) break; 55 ans = 0; 56 for(int i=0; i<maxn; i++) fa[i] = i; 57 for(int i=0; i<M; i++){ 58 int u,v,w; scanf("%d%d%d",&u,&v,&w); 59 E[i].u = u, E[i].v = v, E[i].w = w; 60 } 61 62 kruskal(); 63 64 for(int i=1; i<=N; i++) 65 if(same(1,i) == 0) 66 ans = -1; 67 if(ans == -1) 68 cout << "? "; 69 else 70 cout << ans << endl; 71 } 72 73 return 0; 74 }
Prim：
1 #include <bits/stdc++.h> 2 using namespace std; 3 typedef long long ll; 4 #define MS(a) memset(a,0,sizeof(a)) 5 #define MP make_pair 6 #define PB push_back 7 const int INF = 0x3f3f3f3f; 8 const ll INFLL = 0x3f3f3f3f3f3f3f3fLL; 9 inline ll read(){ 10 ll x=0,f=1;char ch=getchar(); 11 while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} 12 while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();} 13 return x*f; 14 } 15 ////////////////////////////////////////////////////////////////////////// 16 const int maxn = 100+10; 17 18 struct node{ 19 int to,cost; 20 node(int to=0,int cost=0) : to(to),cost(cost) {} 21 bool operator<(const node& rhs)const{ 22 return cost > rhs.cost; 23 } 24 }; 25 26 priority_queue<node> que; 27 std::vector<node> G[maxn]; 28 29 int N,M; 30 bool vis[maxn]; 31 32 ll prim(){ 33 ll res = 0; 34 vis[1] = 1; 35 for(int i=0; i<(int)G[1].size(); i++) 36 que.push(node(G[1][i])); 37 while(!que.empty()){ 38 node e = que.top(); que.pop(); 39 if(vis[e.to]) continue; 40 vis[e.to] = 1; 41 res += e.cost; 42 for(int i=0; i<(int)G[e.to].size(); i++) 43 que.push(G[e.to][i]); 44 } 45 return res; 46 } 47 48 int main(){ 49 while(scanf("%d%d",&M,&N) == 2){ 50 if(M == 0) break; 51 for(int i=0; i<=N; i++) G[i].clear(); 52 while(que.size()) que.pop(); 53 MS(vis); 54 for(int i=1; i<=M; i++){ 55 int u,v,w;scanf("%d%d%d",&u,&v,&w); 56 G[u].push_back(node(v,w)); 57 G[v].push_back(node(u,w)); 58 } 59 60 ll res = prim(); 61 62 for(int i=1; i<=N; i++) 63 if(vis[i] == 0) 64 res = -1; 65 if(res == -1) 66 printf("? "); 67 else 68 printf("%I64d ",res); 69 70 } 71 72 return 0; 73 }