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858. Prim算法求最小生成树
https://www.acwing.com/problem/content/submission/code_detail/7021576/
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AcWing/858/858.cpp
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42
AcWing/858/858.cpp
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#include <bits/stdc++.h>
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using namespace std;
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int n, m, u, v, w, g[505][505], dist[505];
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bool vis[505];
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int prim() {
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memset(dist, 0x3f, sizeof(dist));
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int res = 0;
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for (int i = 0; i < n; i++) {
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int t = -1;
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for (int j = 1; j <= n; j++) {
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if (!vis[j] && (t == -1 || dist[j] < dist[t])) {
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t = j;
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}
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}
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if (i && dist[t] == 0x3f3f3f3f) return 0x3f3f3f3f;
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if (i) res += dist[t];
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for (int j = 1; j <= n; j++) {
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dist[j] = min(dist[j], g[t][j]);
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}
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vis[t] = true;
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}
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return res;
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}
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int main() {
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cin >> n >> m;
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memset(g, 0x3f, sizeof(g));
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for (int i = 0; i < m; i++) {
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cin >> u >> v >> w;
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g[u][v] = g[v][u] = min(g[u][v], w);
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}
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int ans = prim();
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if (ans == 0x3f3f3f3f) {
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cout << "impossible" << endl;
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} else {
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cout << ans << endl;
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}
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return 0;
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}
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