Kruskal算法求最小生成树

Author: Dev-XYS

Kruskal.cpp

@@ -0,0 +1,84 @@
+#include <cstdio>
+#include <algorithm>
+
+#define VERTEX_COUNT 100000
+#define EDGE_COUNT 100000
+
+typedef long long ll;
+
+using namespace std;
+
+struct edge
+{
+	int u, v, w;
+}E[EDGE_COUNT];
+
+int ivc, iec;
+
+int fa[VERTEX_COUNT], size[VERTEX_COUNT];
+
+bool E_cmp(edge x, edge y)
+{
+	return x.w < y.w;
+}
+
+void init_dsu()
+{
+	for (int i = 1; i <= ivc; i++)
+	{
+		fa[i] = i;
+		size[i] = 1;
+	}
+}
+
+int getrt(int x)
+{
+	if (fa[x] == x)
+	{
+		return x;
+	}
+	return (fa[x] = getrt(fa[x]));
+}
+
+void merge(int rtx, int rty)
+{
+	if (size[rtx] < size[rty])
+	{
+		fa[rtx] = rty;
+	}
+	else
+	{
+		fa[rty] = rtx;
+	}
+}
+
+ll Kruskal()
+{
+	int cnt = 1;
+	ll wtotal = 0;
+	for (int i = 0; i < iec && cnt < ivc; i++)
+	{
+		int rtu = getrt(E[i].u), rtv = getrt(E[i].v);
+		if (rtu != rtv)
+		{
+			merge(rtu, rtv);
+			cnt++;
+			wtotal += E[i].w;
+		}
+	}
+	return wtotal;
+}
+
+int main()
+{
+	scanf("%d%d", &ivc, &iec);
+	init_dsu();
+	for (int i = 0; i < iec; i++)
+	{
+		scanf("%d%d%d", &E[i].u, &E[i].v, &E[i].w);
+	}
+	sort(E, E + iec, E_cmp);
+	ll res = Kruskal();
+	printf("%lld", res);
+	return 0;
+}