最小生成树模板

prim:

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int INF = 0x3f3f3f3f;
const int Max = 1e3;
int mp[Max][Max],micost[Max],vis[Max];
int V,E;

int prim()
{
    for(int i=1;i<=V;i++)
    {
        micost[i]=mp[1][i];
        vis[i]=0;
    }
    vis[1]=1;
    int res = 0;
    for(int i=1;i<=V;i++)
    {
        int mi = INF,k = -1;
        for(int j=1;j<=V;j++)
        {
            if(!vis[j]&&mi>micost[j]){
                mi = micost[j];
                k = j;
            }
        }
        if(k==-1) break;
        vis[k]=1;
        res += micost[k];
        for(int j=1;j<=V;j++)
        {
            if(!vis[j]&&micost[j]>mp[k][j])
                micost[j]=mp[k][j];
        }
    }
    return res;
}
int main()
{
    int from,to,cost;
    cin>>V>>E;
    for(int i=1;i<=V;i++)
        for(int j=1;j<=V;j++)
            mp[i][j]=(i==j?0:INF);
    for(int i=0;i<E;i++)
    {
        cin>>from>>to>>cost;
        mp[from][to]=cost;
        mp[to][from]=cost;//不要忘记了
    }
    int ans = prim();
    cout<<ans<<endl;
    return 0;
}

Kruskal: 

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int Max = 1e3;
const int INF = 0x3f3f3f3f;
struct node{
    int from,to,ed;
};
node no[Max];
int V,E;
int par[Max];
int cmp(node e1,node e2)
{
    return e1.ed<e2.ed;
}
void init()
{
    for(int i=1;i<=V;i++)
        par[i]=i;
}
int find(int x)
{
    if(x==par[x]) return x;
    else return par[x]=find(par[x]);
}
void unite(int x,int y)
{
    x = find(x);
    y = find(y);
    if(x!=y)
        par[x]=y;
}
int Kruskal()
{
    sort(no,no+E,cmp);
    init();
    int res = 0;
    for(int i=0;i<E;i++)
    {
        node e = no[i];
        if(find(e.from)!=find(e.to)){
            unite(e.from,e.to);
            res += e.ed;
        }
    }
    return res;
}
int main()
{
    cin>>V>>E;
    for(int i=0;i<E;i++)
        cin>>no[i].from>>no[i].to>>no[i].ed;
    int ans = Kruskal();
    cout<<ans<<endl;
    return 0;
}