AcWing 858. Prim算法求最小生成树
原题链接
简单
作者:
梦都会空
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2021-12-06 18:13:27
,
所有人可见
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阅读 117
#include <iostream>
#include <cstring>
using namespace std;
const int N = 510, INF = 0x3f3f3f3f;
int n, m;
int g[N][N], dist[N];
bool st[N];
int prim() {
memset(dist, INF, sizeof dist);//初始化
int res = 0;
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;
if(i && dist[t] == INF) return INF;
if(i) res += dist[t];
st[t] = true;
for(int j = 1; j <= n; j++)
dist[j] = min(dist[j], g[t][j]);
}
return res;
}
int main() {
cin >> n >> m;
int u, v, w;
for(int i = 1; i <= n; i++)
for(int j = 1; j <= n; j++)
if(i ==j) g[i][j] = 0;
else g[i][j] = INF;
while(m--)
{
cin >> u >> v >> w;
g[u][v] = g[v][u] = min(g[u][v], w);
}
int t = prim();
if(t == INF) puts("impossible");
else cout << t << endl;
return 0;
}