---恢复内容开始--- POJ2976 Dropping tests 这个题就是大白P144页的一个变形,二分枚举x,对a[i]-x*b[i]从大到小进行排序,选取前n-k个判断和是否大于等于0,若满足条件,增大下限,否则,减小下限. 这个题因为精度问题wa了n次,后来干脆把a[i]和b[i]改成double就过了,循环终止条件写成while (abs(ub - lb) > 1e-4)比写成for(int i=0;i<100;i++)要好,既能减少时间消耗,又能满足精度. lb和ub初始化时…

Dropping tests Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 8176   Accepted: 2862 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Given…

Dropping tests   Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 6373   Accepted: 2198 [Description] In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . G…

Dropping tests Time Limit: 1000MS   Memory Limit: 65536K Total Submissions:17069   Accepted: 5925 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Given…

[poj P2976] Dropping tests Time Limit: 1000MS  Memory Limit: 65536K Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Given your test scores and a positi…

Dropping tests Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 4654   Accepted: 1587 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Given…

Dropping tests Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 12187   Accepted: 4257 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Give…

POJ - 2976 Dropping tests 你有 \(n\) 次考试成绩, 定义考试平均成绩为 \[\frac{\sum_{i = 1}^{n} a_{i}}{\sum_{i = 1}^{n} b_{i}}\] 你可以考虑放弃 \(K\) 次成绩, 求最大平均成绩 * 100 小插曲: 被精度卡成喜羊羊 0/1分数规划\(from\)人生导师 Solution 01分数规划(不是很)裸题, 在每次 \(check\) 时, 选取较大的 \(num - K + 1\) 次即可 Code #…

最大化平均值 有n个物品的重量和价值分别wi 和 vi.从中选出 k 个物品使得 单位重量 的价值最大. 限制条件: <= k <= n <= ^ <= w_i <= v_i <= ^6 输入:n = 3k = 2{W, V} = {(2,2), (5,3), (2,1)} 输出:0.75 (如果选0号和2号,平均价格是 (2 + 1) / (2 + 2) = 0.75) 题解: 一般先想到的肯定是:把物品按照  单位价值  进行排序,然后从大到小贪心地进行选取.但是这…

[POJ2976]Dropping Tests(分数规划) 题面 Vjudge 翻译在\(Vjudge\)上有(而且很皮) 题解 简单的\(01\)分数规划 需要我们做的是最大化\(\frac{\sum a[i]}{\sum b[i]}\) 考虑二分答案 将最大化问题转换为判定问题 \(\sum{a[i]}-mid\sum{b[i]}\geq 0\) 因为所有选定的\(i\)是一样的 所以可以将权值化为\(a[i]-mid·b[i]\),这样只需要贪心的选择最大的那部分检查是否大于零就行了 #i…

题目链接:http://poj.org/problem?id=2976 Dropping tests Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 17838   Accepted: 6186 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumula…

题目链接:http://poj.org/problem?id=2976 Dropping tests Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 20830   Accepted: 7052 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumula…

Dropping tests Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 11367   Accepted: 3962 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Give…

题目链接:http://poj.org/problem?id=2976 Dropping tests Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 13615   Accepted: 4780 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumula…

Dropping tests Time Limit: 1000MS Memory Limit: 65536K Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be Given your test scores and a positive integer k, d…

Dropping tests Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 8349   Accepted: 2919 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Given…

P.S.又是一个抽时间学了2个小时的新东西......讲解在上半部分,题解在下半部分. 先说一下转的原文:http://www.cnblogs.com/perseawe/archive/2012/05/03/01fsgh.html我挑选部分转了过来:01分数规划问题 定义:给定两个数组,a[i]表示选取i的收益,b[i]表示选取i的代价.如果选取i,定义x[i]=1否则x[i]=0.每一个物品只有选或者不选两种方案,求一个选择方案使得R=sigma(a[i]*x[i])/sigma(b[i]*x…

Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . . Given your test scores and a positive integer k, determine how high you can make your cumulative aver…

In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Given your test scores and a positive integer k, determine how high you can make your cumulative average if you are…

个人心得:不能说题目太难,而是自己思维太菜,我开始以为这怎么都想不到的,但是学长说不是很简单吗,好吧我信了,我太low. 其实单纯二分只用于搜索,但是这种逆向答案二分确实比较难理解.给大神代码 [一些分析] 数学分析中一个很重要的方法就是分析目标式,这样我们来看目标式. R=sigma(a[i]*x[i])/sigma(b[i]*x[i]) 我们来分析一下他有什么性质可以给我们使用. 我们先定义一个函数F(L):=sigma(a[i]*x[i])-L*sigma(b[i]*x[i]),显然这只是…

Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Given your test scores and a positive integer k, determine how high you can make your cumulative averag…

Time Limit: 1000MSMemory Limit: 65536K Total Submissions: 13849Accepted: 4851 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Given your test scores an…

In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Given your test scores and a positive integer k, determine how high you can make your cumulative average if you are…

http://poj.org/problem?id=2976 Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 13861   Accepted: 4855 Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defi…

Description In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be . Given your test scores and a positive integer k, determine how high you can make your cumulative averag…

题目链接 忽略运算符逻辑导致奇怪的错误(代码中指明位置了) 输出没加0.5,WA. 还有,注意特殊情况k=0,所以scanf("%d%d", &n, &k)&n就够了, scanf("%d%d", &n, &k)&n&k应该会WA. #include <cstdio> #include <cmath> #include <algorithm> using namespace…

最大化平均值 题目大意:给定你n个分数,从中找出k个数,使∑a/∑b的最大值 这一题同样的也可以用二分法来做(用DP会超时,可见二分法是多么的实用呵!),大体上是这样子:假设最大的平均值是w,那么题目就是问存不存在∑a/b>=w,我们把这条式子变形 ∑a-w∑b>=0 那么这一题就变成了寻找k个最大的a-w*b,使∑a-w∑b>=0成立 #include <iostream> #include <algorithm> #include <functional…

题目大概说给n个二元组Ai和Bi,要去掉k个,求余下的100*∑Ai/∑Bi的最大值. 假设要的最大的值是ans,令Di=Ai-ans*∑Bi,对Di排序取最大的n-k个,如果∑Ai-ans*∑Bi>0,说明ans还可以更大,反之ans太大了,所以二分枚举一下ans判断即可. #include<cstdio> #include<cstring> #include<cmath> #include<algorithm> using namespace st…

裸题 看分析请戳这里:http://blog.csdn.net/hhaile/article/details/8883652 #include<stdio.h> #include<algorithm> using namespace std; ; ; int n,k; double a[N],b[N],c[N]; int main() { while(~scanf("%d%d",&n,&k)){ if(!n&&!k)break;…

0/1分数规划问题,用二分解决!! 代码如下: #include<iostream> #include<stdio.h> #include<algorithm> #include<iomanip> #include<cmath> #include<cstring> #define pi acos(-1.0) using namespace std; ],b[],an[]; int main() { int i,j,k,n; doubl…