#分组背包 Educational Codeforces Round 39 (Rated for Div. 2) D. Timetable
2018-03-11
http://codeforces.com/contest/946/problem/D
2 seconds
256 megabytes
standard input
standard output
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.
想法:虽然知道时背包,但是没啥思路,直接戳别人题解的解析:https://www.cnblogs.com/ZERO-/p/8530982.html
一些反思学习吧,有些不应该出现的错误还是会出现。增加刷题量和刷题频率,更重要的是要时时学习巩固算法了。
1.cf显示compication error 可能是头文件错误,比如这题忘写 cstring 而用了memset函数;
2.因为输入的是没有空格的连着的数字,先要将其当成字符;
3.数组越界问题;
4.特判一天的课全部都逃情况;
5.写背包时将计算最小值转化为计算最大值;
6.*怎么去预先处理每组的每种逃课情况下的最小天数(距离),不掌握的话,怕是知道什么算法也使不出来;
7.*学习分组背包;
code
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<iostream>
#include<vector>
#include<queue>
using namespace std;
#define maxn 505
#define fi first
#define se second
#define ll long long
int h[][],p[][];
int num[];
int a[][];
int dp[];
int n,m,k;
char s[][];
int main()
{ cin>>n>>m>>k;
memset(num,,sizeof(num));
for(int i=;i<n;i++)
cin>>s[i];
for(int i=;i<n;i++)
{
for(int j=;j<m;j++)
{
h[i][j]=s[i][j]-'';
if(h[i][j]==)
{num[i]++;a[i][num[i]]=j;} //a[]存第几个1的位置 }
}
for(int i=;i<n;i++) //第几排
{
int tmp=min(k,num[i]);
for(int j=;j<=tmp;j++) //下面要求对应逃课数的最短距离,j是选择的逃课数 j可能为0
{
p[i][j]=maxn; //p存的是最短距离
if(j==num[i]) //易误点:当把全天要上的课逃完时,距离为0,要特判
p[i][j]=;
else
for(int v=;v<=j+;v++) //v是第几节要上的课
{
p[i][j]=min(p[i][j],a[i][v+num[i]-j-]-a[i][v]+);
}
}
}
ll sum=;
for(int i=;i<n;i++)
sum+=p[i][];
memset(dp,,sizeof(dp));
for(int i=;i<n;i++)
//分组背包
for(int j=k;j>=;j--)
for(int v=;v<=min(k,num[i]);v++)
if(j>=v) //一开始没写,数组可能会越界,写上就对了。。。
dp[j]=max(dp[j-v]+p[i][]-p[i][v],dp[j]);
cout<<sum-dp[k]; }
#分组背包 Educational Codeforces Round 39 (Rated for Div. 2) D. Timetable的更多相关文章
- Educational Codeforces Round 39 (Rated for Div. 2) G
Educational Codeforces Round 39 (Rated for Div. 2) G 题意: 给一个序列\(a_i(1 <= a_i <= 10^{9}),2 < ...
- codeforces Educational Codeforces Round 39 (Rated for Div. 2) D
D. Timetable time limit per test 2 seconds memory limit per test 256 megabytes input standard input ...
- Educational Codeforces Round 39 (Rated for Div. 2) 946E E. Largest Beautiful Number
题: OvO http://codeforces.com/contest/946/problem/E CF 946E 解: 记读入串为 s ,答案串为 ans,记读入串长度为 len,下标从 1 开始 ...
- Educational Codeforces Round 39 (Rated for Div. 2) B. Weird Subtraction Process[数论/欧几里得算法]
https://zh.wikipedia.org/wiki/%E8%BC%BE%E8%BD%89%E7%9B%B8%E9%99%A4%E6%B3%95 取模也是一样的,就当多减几次. 在欧几里得最初的 ...
- Educational Codeforces Round 60 (Rated for Div. 2) - C. Magic Ship
Problem Educational Codeforces Round 60 (Rated for Div. 2) - C. Magic Ship Time Limit: 2000 mSec P ...
- Educational Codeforces Round 60 (Rated for Div. 2) - D. Magic Gems(动态规划+矩阵快速幂)
Problem Educational Codeforces Round 60 (Rated for Div. 2) - D. Magic Gems Time Limit: 3000 mSec P ...
- Educational Codeforces Round 43 (Rated for Div. 2)
Educational Codeforces Round 43 (Rated for Div. 2) https://codeforces.com/contest/976 A #include< ...
- Educational Codeforces Round 35 (Rated for Div. 2)
Educational Codeforces Round 35 (Rated for Div. 2) https://codeforces.com/contest/911 A 模拟 #include& ...
- Codeforces Educational Codeforces Round 44 (Rated for Div. 2) F. Isomorphic Strings
Codeforces Educational Codeforces Round 44 (Rated for Div. 2) F. Isomorphic Strings 题目连接: http://cod ...
随机推荐
- python处理u开头的字符串
是用python处理excel过程中,从表格中解析除字符串,打印出来的中文却显示成了u'开头的乱码字符串,在控制台中输出的编码格式是utf-8,而excel表格的数据也是utf-8编码成的,但是解析成 ...
- 实现Ajax异步的layui分页
https://www.e-learn.cn/content/java/1084522
- vue-cli创建第一个项目(用git bash解决上下键移动选择问题)
我电脑是windows:(nodejs已经有了) 1 下载vue-cli cmd 打开命令行,或者是gitbash.最好是用cnpm比较快. 2 创建项目: dos命令,cd 你的希望创建的文件夹 ...
- MySQL数据查询
数据查询语言DQL select [all | distinct] 字段或表达式列表 [from子句] [where子句] [group by子句] [having子句] [order by子句] [ ...
- 注意兼容浮点运算误差 0.7 + 0.1 ==0.8 为false
所以比较 汇总或者计算的时候注意确定精度0.7 + 0.1 ==0.8 换成 Math.abs(0.7 + 0.1 ==0.8)<0.0001参考下
- python全栈开发 * 30知识点汇总 * 180713
30 re模块2一.正则表达式在线测试 在线测试工具 http://tool.chinaz.com/regex/(一).*?的用法: . 是任意字符 * 是取 0 至 无限长度 ? 是非贪婪模式.合在 ...
- JavaScript基础知识(初识JS)
js的组成部分 1. ECMAScript : JS的基础语法 变量 数据类型,操作语句,函数 es3 es5 es6; 2.DOM : document object model : 文档对象模型: ...
- 数组copy
数组copy(推荐用法) System.arraycopy的用法 int[] src = {1,3,5,7,9,11,13,15,17}; int[] dest = {2,4,6,8,10,12,14 ...
- GC垃圾回收器
java与C++之间有一堵由内存动态分配和垃圾收集技术所围成的“高墙”.jvm解决的两个问题:给对象分配内存以及回收分配给对象的内存.GC:将内存中不再被使用的对象进行回收.GC的作用域是JVM运行时 ...
- ubuntu16.04安装libzip库
sudo apt install libzip-dev