prim：

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

const int N = 5000;
int n, m, x, y, z, res;
int e[N+10][N+10], d[N+10];
bool vis[N+10];

ll prim() {
	memset(vis, false, sizeof(vis));
	memset(d, 0x3f3f3f3f, sizeof(d));
	d[1] = 0;
	ll sum = 0;
	for(int i = 1; i <= n; i++) {
		int u = -1;
		for(int v = 1; v <= n; v++) {
			if(vis[v] == false && (u == -1 || d[v] < d[u])) u = v;
		}
		vis[u] = true;
		sum += d[u];
		for(int v = 1; v <= n; v++) {
			if(vis[v] == false) d[v] = min(d[v], e[u][v]);
		}
	}
	return sum;
}

int main() {
	cin >> n >> m;
	memset(e, 0x3f3f3f3f, sizeof(e));
	for(int i = 1; i <= m; i++) {
		cin >> x >> y >> z;
		e[x][y] = z; e[y][x] = z;
	}
	res = prim();
	if(res == 1061109568) cout << "orz";
	else cout << res;
	
	return 0;
}

kruskal：

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

const int N = 5000;
int n, m;
ll res, cnt;
struct Edge {
	int u, v, w;
	bool operator < (Edge o) {
		return w < o.w;
	}
} e[N+10];
int fa[N+10];

void init() {
	cnt = n;
	for(int i = 1; i <= n; i++) fa[i] = i;
}

int find(int u) {
	if(fa[u] == u) return u;
	return fa[u] = find(fa[u]);
}

void merge(int u, int v) {
	u = find(u), v = find(v);
	if(u == v) return;
	fa[u] = v;
	cnt--;
}

ll kruskal() {
	sort(e+1, e+m+1);
	init();
	ll sum = 0;
	for(int i = 1; i <= m; i++) {
		int &u = e[i].u, &v = e[i].v;
		if(find(u) == find(v)) continue;
		merge(u, v);
		sum += e[i].w;
	}
	return (cnt == 1 ? sum : -1);
}

int main() {
	cin >> n >> m;
	for(int i = 1; i <= m; i++) {
		cin >> e[i].u >> e[i].v >> e[i].w;
	}
	res = kruskal();
	if(res == -1) cout << "orz";
	else cout << res;
	
	return 0;
}

怎么办？