https://vjudge.net/problem/POJ-2376 题意理解错了!!真是要仔细看题啊!! 看了poj的discuss才发现,如果前一头牛截止到3,那么下一头牛可以从4开始!!! #include<iostream> #include<cstdio> #include<queue> #include<cstring> #include<algorithm> #include<cmath> #include<se…

题意 POJ2376 Cleaning Shifts 0x50「动态规划」例题 http://bailian.openjudge.cn/practice/2376 总时间限制: 1000ms 内存限制: 65536kB 描述 Farmer John is assigning some of his N (1 <= N <= 25,000) cows to do some cleaning chores around the barn. He always wants to have one c…

POJ2376 Cleaning Shifts Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 14585   Accepted: 3718 Description Farmer John is assigning some of his N (1 <= N <= 25,000) cows to do some cleaning chores around the barn. He always wants to hav…

题目链接: https://vjudge.net/problem/POJ-2376 题目大意: farmer John要安排他的牛清理牛棚,一共有T个牛棚要清理,每头牛可以清理相邻的牛棚.比如,一头牛可以清理4-7号牛棚.当然了,牛清理的牛棚可以重叠.现在要你求出可以完成牛棚的清理的最少头牛的个数,不可以就输出-1. 思路: 贪心题.题目意思很明显是求最少的区间覆盖掉大区间.先对这些时间段排好序(见代码),这个排序应该是没什么问题的.然后呢,第一头牛肯定要选,就从这头牛开始,选取下一头牛.下一头…

http://poj.org/problem?id=2376 john有n头牛做打扫工作,他想在t时间内每个时间都至少有一头牛在做打扫工作,第一头牛在1,最后一头牛在t时间,每一头牛工作都有一个开始时间和结束时间,现在让我们找出在每个时间点都有牛打扫的情况下,所用牛越少越好,不能满足输出-1. 首先按起点排序,起点相同就按结束时间长的排序,然后贪心,每次选择时满足      当前牛的开始时间<=上一头牛的结束时间加1,并且当前牛的结束时间最大的一个. 注意 : 不必覆盖只要能连接即可.(1 3…

最少区间覆盖问题: 首先我们想到将r排序,则以得出dp方程 f[i]=1 (l[i]=1) =min{f[j]}+1 (r[j]+1>=l[i]) 最后ans是min{f[j]} (r[j]>=t); 很显然O(n^2),会超时: 考虑到r已经升序排列,对于一个f[i],如果f[i]<f[j] (i>j) 显然,使用i覆盖比使用j覆盖更优: 于是我们想到用单调队列来优化,维护一个r[j],f[j]都单调增的队列,具体代码如下: ..] of longint;  //w为单调队列,存…

题目: 题目的大概意思是约翰这个农民有N条牛,这些牛可以在一天中的某个时间段可以进行工作,他想把这个时间段分成若干个片段让这些牛去进行打扫任务,你的任务是安排尽量少的牛然后可以完成分成这些片段的打扫任务. 输入: 第一行两个数,第一个数代表牛的个数N,第二个数代表时间T,表示的是时间段[1,T]. 下面的N行每行表示牛工作的时间段. 输出: 输出使用最少的牛的数量. 思路分析:这道题目完全就是一个区间覆盖问题的裸题,求解过程,将每个牛工作的区间按左端点递增排序,如果左端点相同,按右端点递增顺序排…

一.题目 Description Farmer John is assigning some of his N (1 <= N <= 25,000) cows to do some cleaning chores around the barn. He always wants to have one cow working on cleaning things up and has divided the day into T shifts (1 <= T <= 1,000,00…

Cleaning Shifts Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 32561   Accepted: 7972 Description Farmer John is assigning some of his N (1 <= N <= 25,000) cows to do some cleaning chores around the barn. He always wants to have one co…

Cleaning Shifts Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 11542   Accepted: 3004 Description Farmer John is assigning some of his N (1 <= N <= 25,000) cows to do some cleaning chores around the barn. He always wants to have one co…