最小生成树模板

 两种方法：prim:和克鲁斯卡尔，推荐后者。

prim:

 （其实和Dijkstra是一个东西，只有几处代码不同）

#include<cstdio>
#include<cstring>
using namespace std;
int g[310][310];
int n,m,a,b,c,minn[310],mmax=-1;
bool u[310];
int main(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;++i){
        scanf("%d%d%d",&a,&b,&c);
        g[a][b]=c;
        g[b][a]=c;
    }
    memset(minn,0x7f,sizeof(minn));    
    minn[1]=0;
    memset(u,1,sizeof(u));
    for(int i=1;i<=n;++i){
        int k=0;
        for(int j=1;j<=n;j++)
            if(u[j]&&(minn[j]<minn[k]))
                k=j;
        u[k]=0;
        for(int j=1;j<=n;j++)
            if(u[j] && g[k][j]!=0 && g[k][j]<minn[j])
                minn[j]=g[k][j];
    }
    for(int i=1;i<=n;++i){
        if(minn[i]>mmax)
            mmax=minn[i];
    }
    printf("%d %d",n-1,mmax);
    return 0;
}

克鲁斯卡尔：

用了并查集的思想，比较推荐

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
int m, n, u, v, c, maxn, k;
int fa[301];
int find(int x) {
    if(fa[x]!=x) 
        fa[x]=find(fa[x]);
    return fa[x];
}
void unionn(int x,int y) {
    int fx = find(x);
    int fy = find(y);
    if (fx != fy) fa[fx]=fy;
}
struct Node {
    int x, y, v;
    bool operator < (const Node &b) const {
        return v<b.v;
    }
}a[51000];
int main() {
    cin >> n >> m;
    for (int i=1; i<=m; i++) {
        cin >> u >> v >> c;
        a[i]=(Node){u, v, c};
    }
    for (int i=1; i<=n; i++) fa[i]=i;
    sort(a+1,a+m+1);
    for (int i=1; i<=m; i++) {
        if (find(fa[a[i].x]) != find(fa[a[i].y])) {
            unionn(a[i].x, a[i].y);
            maxn = a[i].v;
            k++;
        }
        if (k == n-1) break;
    }
    cout<< n-1 << " " <<maxn; 
    return 0;
}

未完成的Prim堆优化

#include <iostream>
#include <cstdio>
#include <queue>
#define oo 0x7FFFFFFF
using namespace std; 
int n, m, tot, MST;
int d[5001];
int head[5010];
bool vis[5010];

struct rqy {
    int x;
    bool operator < (const rqy &a) const {
        return d[a.x]<d[x]; 
    }
};
priority_queue <rqy> q;

struct Node {
    int data;
    int js;
    int plink;
    Node() { data=plink=js=0; }
}node[20010];

void link(int x,int y, int num) {
    node[++tot].data=num;
    node[tot].plink=head[x];
    node[tot].js=y;
    head[x]=tot;
    return ;
}

int main() {
    cin >> n >> m;
    d[1] = oo; head[1] = 0; vis[1]=1;
    for (int i = 2; i <= n; ++i) {
        d[i]=oo;
        head[i]=0;
        q.push((rqy){i});
    }
    vis[1]=1;
    for (int i=1; i<=m; i++) {
        int u, v, num;
        cin>>u>>v>>num;
        link(u, v, num);
        link(v, u, num);
    }
    for (int i=head[1]; i; i=node[i].plink) 
        d[node[i].js]=node[i].data;
        
    for (int i=1; i<n; i++) {
        int u=q.top().x;
        q.pop();
        MST+=d[u];
        vis[u]=1;
        for (int j=head[u]; j; j=node[j].plink) {
            int v=node[j].js;
            if(!vis[v] && node[j].data < d[v])
                d[v]=node[j].data;
        }
    }
    cout << MST; 
    return 0;
}