构造分组背包(CF)
Ivan is a student at Berland State University (BSU). There are n days in Berland week, and each of these days Ivan might have some classes at the university.
There are m working hours during each Berland day, and each lesson at the university lasts exactly one hour. If at some day Ivan's first lesson is during i-th hour, and last lesson is during j-th hour, then he spends j - i + 1 hours in the university during this day. If there are no lessons during some day, then Ivan stays at home and therefore spends 0 hours in the university.
Ivan doesn't like to spend a lot of time in the university, so he has decided to skip some lessons. He cannot skip more than k lessons during the week. After deciding which lessons he should skip and which he should attend, every day Ivan will enter the university right before the start of the first lesson he does not skip, and leave it after the end of the last lesson he decides to attend. If Ivan skips all lessons during some day, he doesn't go to the university that day at all.
Given n, m, k and Ivan's timetable, can you determine the minimum number of hours he has to spend in the university during one week, if he cannot skip more than k lessons?
The first line contains three integers n, m and k (1 ≤ n, m ≤ 500, 0 ≤ k ≤ 500) — the number of days in the Berland week, the number of working hours during each day, and the number of lessons Ivan can skip, respectively.
Then n lines follow, i-th line containing a binary string of m characters. If j-th character in i-th line is 1, then Ivan has a lesson on i-th day during j-th hour (if it is 0, there is no such lesson).
Print the minimum number of hours Ivan has to spend in the university during the week if he skips not more than k lessons.
2 5 1
01001
10110
5
2 5 0
01001
10110
8
In the first example Ivan can skip any of two lessons during the first day, so he spends 1 hour during the first day and 4 hours during the second day.
In the second example Ivan can't skip any lessons, so he spends 4 hours every day.
题意 : 输入数据有 n 行,代表天数,然后每天有 m 节课, 他可以选择性的翘 K 节课,问最终在校时间最短是多少。
思路分析 : 最开始想的是 3 层 for 的大暴力,每次逃的课一定是某一天的最左或最右的课,但是这样不一定对,可以想一想
后来看了大佬的博客,想明白了,是一个分组背包的问题,我们要做的就是提前预处理出在某一天我们逃 x 节课的所减少的在校时间,当一天的课全部逃后,那么所减少的在校时间就是 m ,然后 3层 for 搞定dp 就ok了
代码示例 :
int n, m, p;
char s[505];
int pos[505][505], num[505];
int c[505][505]; // 删除 k 个字符后的花费最多可以节约的花费
int dp[505]; int main() {
//freopen("in.txt", "r", stdin);
//freopen("out.txt", "w", stdout);
cin >> n >> m >> p;
for(int i = 1; i <= n; i++){
scanf("%s", s+1);
int pp=1;
for(int j = 1; j <= m; j++){
if (s[j] == '1') {num[i]++, pos[i][pp++] = j;}
}
}
for(int i = 1; i <= n; i++){
for(int j = 0; j <= num[i]-1; j++){
int res = inf;
for(int k = 0; k <= num[i]-1; k++){
if (j-k < 0) break;
int q = j - k; // q右边开始选多少个1 k表示左边
res = min(res, pos[i][num[i]-q]-pos[i][k+1]+1);
}
c[i][j] = m-res;
}
c[i][num[i]] = m;
}
//for(int i = 1; i <= n; i++){
//for(int j = 0; j <= m; j++){
//cout << c[i][j] << " " ;
//}
//cout << endl;
//}
for(int i = 1; i <= n; i++){
for(int j = p; j >= 0; j--){
for(int k = 0; k <= min(num[i], j); k++){
dp[j] = max(dp[j], dp[j-k]+c[i][k]);
}
}
//printf("i = %d dp = %d\n",i, dp[p]);
}
cout << n*m-dp[p] << endl;
return 0;
}
构造分组背包(CF)的更多相关文章
- #分组背包 Educational Codeforces Round 39 (Rated for Div. 2) D. Timetable
2018-03-11 http://codeforces.com/contest/946/problem/D D. Timetable time limit per test 2 seconds me ...
- HDU 1712 ACboy needs your help(分组背包)
题意:给你n的课程组,每个课程组有m个课程,每个课程有一个完成时间与价值.问在m天内每组课程组最多选择一个,这样可以得到的最大价值是多少 题解:分组背包,其实就是每个课程组进行01背包,再在课程组内部 ...
- Codeforces Round #383 (Div. 2) D 分组背包
给出一群女孩的重量和颜值 和她们的朋友关系 现在有一个舞台 ab是朋友 bc是朋友 ac就是朋友 给出最大承重 可以邀请这些女孩来玩 对于每一个朋友团体 全邀请or邀请一个or不邀请 问能邀请的女孩的 ...
- HDU 3033 分组背包变形(每种至少一个)
I love sneakers! Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others) ...
- HDU 1712 分组背包
ACboy needs your help Time Limit: 1000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Ot ...
- Codeforces Round #383 (Div. 2) D. Arpa's weak amphitheater and Mehrdad's valuable Hoses(分组背包+dsu)
D. Arpa's weak amphitheater and Mehrdad's valuable Hoses Problem Description: Mehrdad wants to invit ...
- HDU3535AreYouBusy[混合背包 分组背包]
AreYouBusy Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)Total ...
- POJ1837 Balance[分组背包]
Balance Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 13717 Accepted: 8616 Descript ...
- Codevs1378选课[树形DP|两种做法(多叉转二叉|树形DP+分组背包)---(▼皿▼#)----^___^]
题目描述 Description 学校实行学分制.每门的必修课都有固定的学分,同时还必须获得相应的选修课程学分.学校开设了N(N<300)门的选修课程,每个学生可选课程的数量M是给定的.学生选修 ...
随机推荐
- 2019-4-12-WPF-绑定的默认模式
title author date CreateTime categories WPF 绑定的默认模式 lindexi 2019-04-12 09:38:58 +0800 2019-04-12 09: ...
- 【codeforces 761C】Dasha and Password(动态规划做法)
time limit per test2 seconds memory limit per test256 megabytes inputstandard input outputstandard o ...
- P1077 旅行
题目描述 你要进行一个行程为7000KM的旅行,现在沿途有些汽车旅馆,为了安全起见,每天晚上都不开车,住在汽车旅馆,你手里现在已经有一个旅馆列表,用离起点的距离来标识,如下: 0, 990, 1010 ...
- tensorflow在文本处理中的使用——Word2Vec预测
代码来源于:tensorflow机器学习实战指南(曾益强 译,2017年9月)——第七章:自然语言处理 代码地址:https://github.com/nfmcclure/tensorflow-coo ...
- 一个vue管理系统的初步搭建总结
ps:目前这个项目只是有一个大致的框架,并没有做完 前期准备工作 前端构建工具:Visual Studio Code后端构建工具:IDEA数据库和服务器构建工具:WampServer (使用的是2.4 ...
- SSI(服务器端嵌入)
简介 SSI(服务器端嵌入)是一组放在 HTML 页面中的指令,当服务器向客户端访问提供这些页面时,会解释执行这些指令.它们能为已有的 HTML 页面添加动态生成内容,不需要通过 CGI 程序来或其他 ...
- 王雅超的学习笔记-大数据hadoop集群部署(七)
MySQL的安装部署
- MySQL数据库性能优化:表、索引、SQL等
一.MySQL 数据库性能优化之SQL优化 注:这篇文章是以 MySQL 为背景,很多内容同时适用于其他关系型数据库,需要有一些索引知识为基础 优化目标 减少 IO 次数IO永远是数据库最容易瓶颈的地 ...
- $Noip2015/Luogu2661$ 信息传递 并查集
Luogu $Description$ 给定一个有向图,每个点只有一条出边.求图里的最小环. $Sol$ 使得这个题不难的地方就在于每个点只有一条出边叭. 一边连边一边更新答案.首先当然是初始$f[i ...
- 敏捷开发:代码Review
热情高涨 代码走查作为一种流程形式,起初大家的参与热情非常高涨. 因为,自己可以学习到别人一些巧妙的思想,自己的代码和习惯都暴漏出来. 这个过程中不断地吸收和改正. 但是...... 我们一开始组织的 ...