[题意]每条路径有一个 cost 和 dist,求图中 sigma(cost) / sigma(dist) 最小的生成树. 标准的最优比率生成树,楼教主当年开场随手1YES然后把别人带错方向的题Orz-- ♦01分数规划 参考Amber-胡伯涛神牛的论文<最小割模型在信息学竞赛中的应用> °定义 分数规划(fractional programming)的一般形式: Minimize  λ = f(x) = a(x) / b(x)   ( x∈S  && ∀x∈S, b(x) &…

Desert King Time Limit: 3000MS   Memory Limit: 65536K Total Submissions:29775   Accepted: 8192 Description David the Great has just become the king of a desert country. To win the respect of his people, he decided to build channels all over his count…

一个完全图,每两个点之间的cost是海拔差距的绝对值,长度是平面欧式距离, 让你找到一棵生成树,使得树边的的cost的和/距离的和,比例最小 然后就是最优比例生成树,也就是01规划裸题 看这一发:http://blog.csdn.net/sdj222555/article/details/7490797 #include<stdio.h> #include<algorithm> #include<math.h> #include<queue> #includ…

题目: http://poj.org/problem?id=2728 题解: 二分比率,然后每条边边权变成w-mid*dis,用prim跑最小生成树就行 #include<cstdio> #include<algorithm> #include<cstring> #include<cmath> #define N 1005 using namespace std; int n,tot; double x[N],y[N],z[N],dis[N]; bool v…

题目:http://poj.org/problem?id=2728 第一道01分数规划题!(其实也蛮简单的) 这题也可以用迭代做(但是不会),这里用了二分: 由于比较裸,不作过多说明了. 代码如下: #include<iostream> #include<cstdio> #include<cstring> #include<cmath> #define eps 1e-6 using namespace std; int const inf=0x3f3f3f;…

Desert King Time Limit: 3000MS   Memory Limit: 65536K Total Submissions: 21766   Accepted: 6087 Description David the Great has just become the king of a desert country. To win the respect of his people, he decided to build channels all over his coun…

Description David the Great has just become the king of a desert country. To win the respect of his people, he decided to build channels all over his country to bring water to every village. Villages which are connected to his capital village will be…

这题数据量较大.普通的求MST是会超时的. d[i]=cost[i]-ans*dis[0][i] 据此二分. 但此题用Dinkelbach迭代更好 #include<cstdio> #include<cstring> #include<cmath> #include<iostream> #include<algorithm> using namespace std; #define N 1010 double mp[N][N],c[N][N],x…

[POJ2728]Desert King(分数规划) 题面 vjudge 翻译: 有\(n\)个点,每个点有一个坐标和高度 两点之间的费用是高度之差的绝对值 两点之间的距离就是欧几里得距离 求一棵生成数,使得单位距离的费用最小 题解 使得\(\sum cost/\sum dis\)最小 这是分数规划问题 二分答案\(K\) 如果\(K\)满足,则有 \(\sum cost-K\sum dis\leq 0\) 定义生成树边权为\(cost-K·dis\) 做最小生成树检查答案即可. 因为是稠密图,…

http://poj.org/problem?id=2728 题意: 在这么一个图中求一棵生成树,这棵树的单位长度的花费最小是多少? 思路: 最优比率生成树,也就是01分数规划,二分答案即可,题目很简单,因为这题是稠密图,所以用prim算法会好点. #include<iostream> #include<algorithm> #include<cstring> #include<cstdio> #include<vector> #include&…