模板

克鲁斯卡尔

#include <cstdio>
#include <algorithm>
using namespace std;
#define maxn 200005
#define ll long long
int fa[maxn], n, m;
struct Edge
{
    int x;
    int y;
    int z;
} edge[maxn];
bool cmp(Edge a,Edge b)
{
    return a.z < b.z;
}
int Find(int x)
{
    if(x==fa[x])
        return x;
    else
        return fa[x] = Find(fa[x]);
}
int main()
{
    scanf("%d%d", &n, &m);
    int ans = 0;
    for (int i = 1; i <= m;i++)
    {
        scanf("%d%d%d", &edge[i].x, &edge[i].y, &edge[i].z);
    }
    sort(edge + 1, edge + 1 + m,cmp);
    for (int i = 1; i <= n;i++)
        fa[i] = i;
    for (int i = 1; i <= m;i++)
    {
        int x = Find(edge[i].x);
        int y = Find(edge[i].y);
        if(x==y)
            continue;
        fa[x] = y;
        ans += edge[i].z;
    }
    printf("%d
",ans);
    system("pause");
}

　　

普里姆

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define maxn1 100005
#define maxn2 3005
#define ll long long
int a[maxn2][maxn2], d[maxn1], n, m, ans;
bool vis[maxn2][maxn2];
void Prim()
{
	memset(d, 0x3f, sizeof(d));
	memset(vis, 0, sizeof(vis));
	d[1] = 0;
	for (int i = 1; i < n;i++)
	{
		int x = 0;
		for (int j = 1; j <= n;j++)
			if(!vis[j]&&(x==0||d[j]<d[x]))
				x = j;
		vis[x] = 1;
		for (int y = 1; y <= n;y++)
			if(!vis[y])
				d[y] = min(d[y], a[x][y]);
	}
}
int main()
{
	scanf("%d%d", &n, &m);
	memset(a,0x3f,sizeof(a));
	for (int i = 1; i <= n;i++)
		a[i][i] = 0;
	for (int i = 1; i <= m;i++)
	{
		int x, y, z;
		scanf("%d%d%d", &x, &y, &z);
		a[x][y] = a[y][x] = min(z, a[x][y]);   //有些题两点之间会有重边
	}
	Prim();
	for (int i = 2; i <= n;i++)
		ans += d[i];
	printf("%d
", ans);
}