AcWing 858. Prim算法求最小生成树
原题链接
简单
作者:
整天睡大觉
,
2024-03-14 12:13:50
,
所有人可见
,
阅读 8
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 510, INF = 0x3f3f3f3f;
int n, m;
int g[N][N];
int dist[N];
bool st[N];
int prime(){
memset(dist, 0x3f, sizeof dist);
int res = 0;
//将n个点选入集合中,所以有n次循环
for(int i = 0; i < n; i ++){
int t = -1;
for(int j = 1; j <= n; j ++){
if(!st[j] && (t == -1 || dist[t] > dist[j])){
t = j;
}
}
//若没有点与集合连通
if(i && dist[t] == INF) return INF;
if (i) res += dist[t];
st[t] = true;
//更新点到集合的最短距离
for (int j = 1; j <= n; j ++ ){
dist[j] = min(dist[j], g[t][j]);
}
}
return res;
}
int main()
{
scanf("%d%d", &n, &m);
memset(g, 0x3f, sizeof g);
while (m -- ){
int a, b, c;
scanf("%d%d%d", &a, &b, &c);
g[a][b] = g[b][a] = min(g[a][b], c);
}
int t = prime();
if(t == INF) puts("impossible");
else printf("%d", t);
return 0;
}