Create 1947_infnty.cpp

From GitHub : https://github.com/infnty/acm/blob/master/acm.pku.edu.cn/1947.cc

POJ/1947_infnty.cpp

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+#include <cstdio>
+#include <cstring>
+#include <cassert>
+#include <algorithm>
+#include <sstream>
+#include <vector>
+using namespace std;
+#define REP(i,n) for(int _REP_N=(n),i=0;i<_REP_N;i++)
+
+int N, parent[200], kid[200], sib[200], memo[200][200], INF=1<<25;
+vector<int> adj[200];
+
+int g(int x, int k);
+
+int f(int x, int k) {
+	int &res = memo[x][k];
+	if (res != -1) return res;
+
+	if (x == 0) return res = (k==0 ? 0 : INF);
+
+	assert(2 <= x && x <= N && k >= 0);
+
+	res = 1 + f(sib[x], k);
+
+	for (int u = 1; u <= k; u++)
+		res <?= g(x, u) + f(sib[x], k-u);
+	return res;
+}
+
+int g(int x, int k) {
+	assert(1 <= x && x <= N && k >= 0);
+	int deg = adj[x].size() - (x==1 ? 0 : 1);
+	if (k == 0) return 0;
+	if (k == 1) return deg;
+	if (deg == 0) return INF;
+	return f(kid[x], k-1);
+}
+
+void dfs(int x, int p) {
+	parent[x] = p;
+	kid[x] = 0;
+
+	REP(i, adj[x].size()) {
+		int y = adj[x][i];
+		if (y != p) {
+			sib[y] = kid[x];
+			kid[x] = y;
+			dfs(y, x);
+		}
+	}
+}
+
+int main() {
+	int P;
+	scanf("%d %d", &N, &P);
+	REP(i, N-1) {
+		int x, y;
+		scanf("%d %d", &x, &y);
+		adj[x].push_back(y);
+		adj[y].push_back(x);
+	}
+
+	kid[0] = sib[0] = parent[0] = 0;
+	dfs(1, 0);
+
+	memset(memo, 0xff, sizeof(memo));
+
+	int res = INF;
+	for (int x = 1; x <= N; x++)
+		res <?= g(x,P) + (x==1 ? 0 : 1);
+	printf("%d\n", res);
+}