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858. Prim算法求最小生成树

https://www.acwing.com/problem/content/submission/code_detail/7021576/
This commit is contained in:
Baoshuo Ren 2021-08-10 10:53:07 +08:00 committed by Baoshuo Ren
parent 0895f652d6
commit b399828300
Signed by: baoshuo
GPG Key ID: 70F90A673FB1AB68

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AcWing/858/858.cpp Normal file
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#include <bits/stdc++.h>
using namespace std;
int n, m, u, v, w, g[505][505], dist[505];
bool vis[505];
int prim() {
memset(dist, 0x3f, sizeof(dist));
int res = 0;
for (int i = 0; i < n; i++) {
int t = -1;
for (int j = 1; j <= n; j++) {
if (!vis[j] && (t == -1 || dist[j] < dist[t])) {
t = j;
}
}
if (i && dist[t] == 0x3f3f3f3f) return 0x3f3f3f3f;
if (i) res += dist[t];
for (int j = 1; j <= n; j++) {
dist[j] = min(dist[j], g[t][j]);
}
vis[t] = true;
}
return res;
}
int main() {
cin >> n >> m;
memset(g, 0x3f, sizeof(g));
for (int i = 0; i < m; i++) {
cin >> u >> v >> w;
g[u][v] = g[v][u] = min(g[u][v], w);
}
int ans = prim();
if (ans == 0x3f3f3f3f) {
cout << "impossible" << endl;
} else {
cout << ans << endl;
}
return 0;
}