858. Prim算法求最小生成树

https://www.acwing.com/problem/content/submission/code_detail/7021576/

AcWing/858/858.cpp

@@ -0,0 +1,42 @@
+#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;
+}