luogu p3366 最小生成树模板

倒腾了一个小时  自己也没去看网上的

总算自己能写出来模板了

kruskal

//最小生成树  每次找最短的边
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = ;
int n,m;
ll res;
struct node
{
    int st,e;
    int cost;
}E[maxn];//建立边
int fa[maxn];

void init()
{
    for(int i=;i<=n;i++)
        fa[i] = i;
}

int fi(int x)
{
    return fa[x] == x? x : fa[x] = fi(fa[x]);
}

void join(int x,int y)
{
    int fx =fi(x),fy = fi(y);
    if(fx != fy)
    {
        fa[fx] = fy;
    }
}

bool same(int x,int y)
{
    return fi(x) == fi(y);
}
bool cmp(node a,node b)
{
    return a.cost < b.cost;
}

void solve()
{
    init();
    res = ;
    sort(E+,E++m,cmp);
    for(int i=;i<=m;i++)
    {
        node now = E[i];
        if(same(now.st,now.e))
            continue; //之前建立过边的 直接跳过
        join(now.st,now.e);
        res += E[i].cost;
    }
}

int main()
{
    //freopen("in.txt","r",stdin);
    while (~scanf("%d %d",&n,&m) )
    {
        for(int i=;i<=m;i++)
        {
            int x,y,v;
            scanf("%d %d %d",&x,&y,&v);
            E[i].st = x;
            E[i].e = y;
            E[i].cost = v;
        }
        solve();
        bool flag = ;
        for(int i=;i<=n;i++)
        {
            if(!same(,i))
            {
                flag =;break;
            }
        }
        if(flag)
            puts("orz");
        else
            cout<<res<<endl;
    }
}

prim

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = ;
struct node {
    int to,cost;
    node (int t,int c):to(t),cost(c){}
    bool operator<(const node& l)const
    {
        return cost > l.cost;
    }
};
vector<node> E[maxn];
priority_queue<node> Q;
bool vis[maxn];
ll d[maxn];
int main ()
{
    int n,m;
    cin>> n>>m;
    for(int i=;i<=m;i++)
    {
        int x,y,v;
        scanf("%d %d %d",&x,&y,&v);
        E[x].push_back({y,v});
        E[y].push_back({x,v});
    }
    for(int i=;i<E[].size();i++)
        Q.push(E[][i]);
    d[] = ;vis[] = ;
    ll res=;
    while (Q.size())
    {
        node now = Q.top();
        Q.pop();
        if(vis[now.to])
            continue;
        res += now.cost;
        vis[now.to] =;
        for(int i=;i <E[now.to].size();i++)
        {
            Q.push(E[now.to][i]);
        }
    }
    bool flag = ;
    for(int i=;i<=n;i++)
    {
        if(!vis[i])
        {
            flag =;
            break;
        }
    }
    if(flag )
        puts("orz");
    else
        cout<<res<<endl;
}