最小生成树入门（克鲁斯卡尔+普利姆 hdu1233）

克鲁斯卡尔

#include <set>
#include <map>
#include <queue>
#include <stack>
#include <math.h>
#include <bitset>
#include <vector>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#define MAXN 1010100
#define LL long long
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define ll __int64
#define INF 0x7fffffff
#define cs(s) freopen(s,"r",stdin)
#define mem(x) memset(x,0,sizeof(x))
#define PI acos(-1)
#define eps 1e-10
using namespace std;
int gcd(int a,int b){return b?gcd(b,a%b):a;}
int lcm(int a,int b){return a/gcd(a,b)*b;}
LL powmod(LL a,LL b,LL MOD){LL ans=1;while(b){if(b%2)ans=ans*a%MOD;a=a*a%MOD;b/=2;}return ans;}
//head
int n,m;
int f[10001];
int find(int x){
	return x==f[x]?x:f[x]=find(f[x]);
}
struct uzi
{
	int l,r,w;
	bool operator <(const uzi & t)const {
		return w<t.w;
	}
};
vector<uzi>v;
void init(){
	v.clear();
	for(int i=1;i<=n;i++)f[i]=i;
}
int main(){
	// freopen("in.txt","r",stdin);
	// freopen("out.txt","w",stdout);
	ios::sync_with_stdio(false);
	while(cin>>n&&n){
		init();
		for(int i=1;i<=n*(n-1)/2;i++){
			int l,r,w;
			cin>>l>>r>>w;
			v.pb({l,r,w});
		}
		int sum=0,cnt=0;
		sort(v.begin(), v.end());
		for(int i=0;i<v.size();i++){
			uzi k=v[i];
			int x=find(k.l),y=find(k.r);
			if(x==y)continue;
			f[y]=x;
			sum+=k.w;
			if((++cnt)==n-1)break;
		}
		cout<<sum<<endl;
	}
	return 0;
}

普利姆

#include <set>
#include <map>
#include <queue>
#include <stack>
#include <math.h>
#include <bitset>
#include <vector>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#define MAXN 1010100
#define LL long long
#define fi first
#define se second
#define mp make_pair
#define pi pair<int,int>
#define pb push_back
#define INF 0x7fffffff
#define cs(s) freopen(s,"r",stdin)
#define mem(x) memset(x,0,sizeof(x))
#define PI acos(-1)
#define eps 1e-10
using namespace std;
int gcd(int a,int b){return b?gcd(b,a%b):a;}
int lcm(int a,int b){return a/gcd(a,b)*b;}
LL powmod(LL a,LL b,LL MOD){LL ans=1;while(b){if(b%2)ans=ans*a%MOD;a=a*a%MOD;b/=2;}return ans;}
//head
int t,n,m,s,w;
int a[101][101],vis[101],dis[101];
void gao(){
	for(int i=1;i<=n;i++)vis[i]=0,dis[i]=INF;
	dis[1]=0;
	int ans=0;
	for(int i=1;i<=n;i++){
		int mark=-1;
		for(int j=1;j<=n;j++){
			if(!vis[j]){
				if(mark==-1)mark=j;
				else if(dis[j]<dis[mark])mark=j;
			}
		}
		if(mark==-1)break;
		ans+=dis[mark];
		vis[mark]=1;
		for(int j=1;j<=n;j++){
			if(!vis[j])dis[j]=min(dis[j],a[mark][j]);
		}
	}
	cout<<ans<<endl;
	return ;
}
int main(){
	ios::sync_with_stdio(false);
	while(cin>>n&&n){
		for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)a[i][j]=INF;
		for(int i=1;i<=n*(n-1)/2;i++)cin>>s>>t>>w,a[s][t]=a[t][s]=w;
		gao();
	}
	return 0;
}