【题解】CF1085D：Minimum Diameter Tree

原题传送门
贪心，只给与叶子结点相连的边赋值，平均分
假设有 $cnt$个叶子，每条叶子边的权值为 $\frac{s}{cnt}$
答案是 $2\frac{s}{cnt}$

Code：

#include <bits/stdc++.h>
#define maxn 100010
using namespace std;
double s, cnt;
int n, d[maxn];

inline int read(){
	int s = 0, w = 1;
	char c = getchar();
	for (; !isdigit(c); c = getchar()) if (c == '-') w = -1;
	for (; isdigit(c); c = getchar()) s = (s << 1) + (s << 3) + (c ^ 48);
	return s * w;
}

int main(){
	n = read(), s = read();
	for (int i = 1; i < n; ++i) ++d[read()], ++d[read()];
	for (int i = 1; i <= n; ++i) cnt += (d[i] == 1);
	printf("%.12lf\n", 2.0 * s / cnt);
	return 0;
}