最小生成树（prim）普通算法及堆优化

// Luogu P3366 【模板】最小生成树

include

include

include

include

define inf 1e9

using namespace std;

int n,m,a,b,c,ans,cnt;
const int N=5010;
struct edge{int v,w;};
vector e[N];
int d[N], vis[N];

bool prim(int s){
for(int i=0;i<=n;i++)d[i]=inf;
d[s]=0;
for(int i=1;i<=n;i++){
int u=0;
for(int j=1;j<=n;j++)
if(!vis[j]&&d[j]<d[u]) u=j;
vis[u]=1; //标记u已出圈
ans+=d[u];
if(d[u]!=inf) cnt++;
for(auto ed : e[u]){
int v=ed.v, w=ed.w;
if(d[v]>w) d[v]=w;
}
}
return cnt==n;
}
int main(){
cin>>n>>m;
for(int i=0; i<m; i++){
cin>>a>>b>>c;
e[a].push_back({b,c});
e[b].push_back({a,c});
}
if(!prim(1))puts("orz");
else printf("%d\n",ans);
return 0;
}

///////////////////Heap-Prim

include

include

include

include

define inf 1e9

using namespace std;

const int N=5010;
int n,m,a,b,c,ans,cnt;
struct edge{int v,w;};
vector e[N];
int d[N], vis[N];
priority_queue<pair<int,int>> q;

bool prim(int s){
for(int i=0;i<=n;i++) d[i]=inf;
d[s]=0; q.push({0,s});
while(q.size()){
int u=q.top().second; q.pop();
if(vis[u])continue;//再出队跳过
vis[u]=1;//标记u已出队
ans+=d[u]; cnt++;
for(auto ed : e[u]){
int v=ed.v, w=ed.w;
if(d[v]>w){
d[v]=w;
q.push({-d[v],v});//大根堆
}
}
}
return cnt==n;
}
int main(){
cin>>n>>m;
for(int i=0; i<m; i++){
cin>>a>>b>>c;
e[a].push_back({b,c});
e[b].push_back({a,c});
}
if(!prim(1))puts("orz");
else printf("%d\n",ans);
return 0;
}