```cpp
#include<iostream>
#include<cstring>
using namespace std;
const int maxn = 5010;
int n, m, cnt, ans;
int dis[maxn], vis[maxn], head[maxn];
struct edge {
int to, nxt, w;
}e[400010]; //双向边等于两条，容量*2;
void init() { //初始化
for(int i = 1; i <= n; i ++)
dis[i] = 1e9;
memset(head, -1, sizeof(head));
ans = 0;
}
void add(int u, int v, int w) { //链式前向星存边
e[++cnt].to = v;
e[cnt].w = w;
e[cnt].nxt = head[u];
head[u] = cnt;
}
void prim() { //prim算法
dis[1] = 0;
dis[0]=1e9;//1.打擂台的时候初始值要大。
for(int i = 1; i <= n; i ++) {
int k = 0;
for(int j = 1; j <= n; j ++)
if(!vis[j] && dis[j] < dis[k])
k = j;
vis[k] = 1;
ans += dis[k];
for(int j = head[k]; ~j; j = e[j].nxt) {
int v = e[j].to;
if(!vis[v] && dis[v] > e[j].w)//2.是vis[v]而不是vis[j]
dis[v] = e[j].w;//3.是e[j].w!
}
}
}
int main() {
cin >> n >> m;
init();
for(int i = 1; i <= m; i ++) {
int u, v, w;
cin >> u >> v >> w;
add(u, v, w);
add(v, u, w); //双向边
}
prim(); //prim最小生成树算法
if(ans == 0) cout << "orz" << endl;
else cout << ans << endl;
return 0;
}
```
by __zaa__ @ 2024-02-22 17:16:16
@[Suin_tryin](/user/936388)
by __zaa__ @ 2024-02-22 17:16:30
### 非常感谢，现在已经AC了
prim()里还要加一个特判，不然改了以后 #13 还是过不了
```cpp
if(k == 0) {
ans = 0;
break;
}
```
by Suin_tryin @ 2024-02-22 17:32:48