将树转化为Prüfer序列

Author: Dev-XYS

Prüfer-Sequence(Tree-to-Sequence).cpp

@@ -0,0 +1,86 @@
+#include <cstdio>
+#include <queue>
+
+#define VERTEX_COUNT 100010
+#define EDGE_COUNT 200010
+
+using namespace std;
+
+struct vertex
+{
+	int first, subcnt, fa;
+	bool vis;
+}V[VERTEX_COUNT];
+
+struct edge
+{
+	int endp, next;
+}E[EDGE_COUNT];
+
+int ivc, ec = 2, prufer[VERTEX_COUNT], pc;
+priority_queue< int, vector<int>, greater<int> > Q;
+
+inline void add_edge(int u, int v)
+{
+	E[ec].next = V[u].first;
+	V[u].first = ec;
+	E[ec].endp = v;
+	ec++;
+}
+
+void dfs(int u, int fa)
+{
+	V[u].vis = true;
+	V[u].fa = fa;
+	for (int cur = V[u].first; cur != 0; cur = E[cur].next)
+	{
+		if (V[E[cur].endp].vis == false) dfs(E[cur].endp, u), V[u].subcnt++;
+	}
+}
+
+int main()
+{
+	int u, v;
+	scanf("%d", &ivc);
+	for (int i = 1; i < ivc; i++)
+	{
+		scanf("%d%d", &u, &v);
+		add_edge(u, v);
+		add_edge(v, u);
+	}
+	dfs(1, 0);
+	for (int i = 1; i <= ivc; i++)
+	{
+		if (E[V[i].first].next == 0) Q.push(i);
+	}
+	for (int i = 3; i <= ivc; i++)
+	{
+		int u = Q.top();printf("pop : %d, fa = %d\n", u, V[u].fa);
+		Q.pop();
+		if (V[u].fa == 0)
+		{
+			for (int cur = V[u].first; cur != 0; cur = E[cur].next)
+			{
+				if (V[E[cur].endp].fa != 0)
+				{
+					prufer[pc++] = E[cur].endp;
+					V[E[cur].endp].fa = 0;
+					if (V[E[cur].endp].subcnt == 1) Q.push(E[cur].endp);
+					break;
+				}
+			}
+		}
+		else
+		{
+			prufer[pc++] = V[u].fa;
+			V[V[u].fa].subcnt--;
+			if (V[V[u].fa].subcnt == 0) Q.push(V[u].fa);
+			else if (V[V[u].fa].subcnt == 1 && V[V[u].fa].fa == 0) Q.push(V[u].fa);
+		}
+	}
+	for (int i = 0; i < pc; i++)
+	{
+		printf("%d ", prufer[i]);
+	}
+	return 0;
+}