Best Cow Fences Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 14601 Accepted: 4720 Description Farmer John's farm consists of a long row of N (1 <= N <= 100,000)fields. Each field contains a certain number of cows, 1 <= ncows <= 2…

Best Cow Fences Time Limit: 1000MS Memory Limit: 30000K Description Farmer John's farm consists of a long row of N (1 <= N <= 100,000)fields. Each field contains a certain number of cows, 1 <= ncows <= 2000. FJ wants to build a fence around a…

题目链接:http://poj.org/problem?id=2018 题目给了一些农场,每个农场有一定数量的奶牛,农场依次排列,问选择至少连续排列F个农场的序列,使这些农场的奶牛平均数量最大,求最大数量*1000/农场的个数. 思路:题目是求是否存在一个长度不小于F的子段,使得平均数最大. 1.用二分法从给定数据的最小平均数到最大平均数进行二分枚举,每次枚举的平均值为mid,那么子段的每一个元素减去mid值再求和应当大于0,否则不满足题意,这样可以不断地二分,最终找到最大的mid值 2.判断子…

$ POJ~2018~Best~Cow~ Fences $(二分答案构造新权值) $ solution: $ 题目大意: 给定正整数数列 $ A $ ,求一个平均数最大的长度不小于 $ L $ 的子段 这道题首先我们如果没有长度限制,直接扫一遍数组即可 而有了长度限制之后我们的候选集合发生改变,很容让我们想到DP 事实上这一道题可以DP,用斜率优化复杂度极小,就是有点常数(事实上最优) 但是我们可以参考类似01规划的做法,因为答案具有单调行. 我们让数组中每一个数都减去我们二分答案枚举的值,然后…

题意:给出长度>=f的最大连续区间平均数 思路:二分这个平均数,然后O(n)判断是否可行,再调整l,r.判断方法是,先求出每个数对这个平均数的贡献,再求出长度>=f的最大贡献的区间,如果这个最大贡献大于0说明这个二分出来的数可行. 代码: #include<set> #include<map> #include<stack> #include<cmath> #include<queue> #include<vector>…

斜率优化. 设$s[i]$表示前缀和,$avg(i,j)=(s[j]-s[i-1])/(j-(i-1))$.就是$(j,s[j])$与$(i-1,s[i-1])$两点之间的斜率. 如果,我们目前在计算$px$与哪个点相连斜率最大,那么一定不会是$pj$点.因为不是$pi$比优就是$pk$比$pi$优.因此斜率优化可以将$pj$这样的点直接删除. 因此队列里存着的相邻两点的斜率是不断增大的. 因为$(s[i+1]-s[i])/1$是大于等于$1$的,所以如果$pi$点与$pt$点形成的斜率最大,那…

POJ 3617 Best Cow Line Time Limit: 1000MS Memory Limit: 65536K [Description] [题目描述] FJ is about to take his N (1 ≤ N ≤ 2,000) cows to the annual "Farmer of the Year" competition. In this contest every farmer arranges his cows in a line and herds…

POJ 3268 Silver Cow Party (最短路径) Description One cow from each of N farms (1 ≤ N ≤ 1000) conveniently numbered 1..N is going to attend the big cow party to be held at farm #X (1 ≤ X ≤ N). A total of M (1 ≤ M ≤ 100,000) unidirectional (one-way roads c…

Best Cow Fences Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 10174 Accepted: 3294 Description Farmer John's farm consists of a long row of N (1 <= N <= 100,000)fields. Each field contains a certain number of cows, 1 <= ncows <= 2…

POJ 3268 Silver Cow Party Description One cow from each of N farms (1 ≤ N ≤ 1000) conveniently numbered 1..N is going to attend the big cow party to be held at farm #X (1 ≤ X ≤ N). A total of M (1 ≤ M ≤ 100,000) unidirectional (one-way roads connects…