CF 154 div2 B(dp)

B. Physics Practical
time limit per test
1 second
memory limit per test
256 megabytes
input
input.txt
output
output.txt

One day Vasya was on a physics practical, performing the task on measuring the capacitance. He followed the teacher's advice and did as much as n measurements, and recorded the results in the notebook. After that he was about to show the results to the teacher, but he remembered that at the last lesson, the teacher had made his friend Petya redo the experiment because the largest and the smallest results differed by more than two times. Vasya is lazy, and he does not want to redo the experiment. He wants to do the task and go home play computer games. So he decided to cheat: before Vasya shows the measurements to the teacher, he will erase some of them, so as to make the largest and the smallest results of the remaining measurements differ in no more than two times. In other words, if the remaining measurements have the smallest result x, and the largest result y, then the inequality y ≤ 2·x must fulfill. Of course, to avoid the teacher's suspicion, Vasya wants to remove as few measurement results as possible from his notes.

Help Vasya, find what minimum number of measurement results he will have to erase from his notes so that the largest and the smallest of the remaining results of the measurements differed in no more than two times.

Input

The first line contains integer n (2 ≤ n ≤ 105) — the number of measurements Vasya made. The second line contains n integersc1, c2, ..., cn (1 ≤ ci ≤ 5000) — the results of the measurements. The numbers on the second line are separated by single spaces.

Output

Print a single integer — the minimum number of results Vasya will have to remove.

Sample test(s)
input
6
4 5 3 8 3 7
output
2
input
4
4 3 2 4
output
0
Note

In the first sample you can remove the fourth and the sixth measurement results (values 8 and 7). Then the maximum of the remaining values will be 5, and the minimum one will be 3. Or else, you can remove the third and fifth results (both equal 3). After that the largest remaining result will be 8, and the smallest one will be 4.

容易看出是根据首尾位置来进行dp,但n的范围很大,n^2是不行的,注意c的范围很小,这样可以记下1-5000所有数出现的个数,然后dp下标是1-5000的数,就可以了。

#include<cstdio>
#include<cstring>
#include<queue>
#include<vector>
#include<algorithm>
#include<iostream>
using namespace std;

const int maxn = 5000 + 5;

int c[maxn],dp[maxn][maxn];

int Dp(int l,int r){
    if(dp[l][r] != -1) return dp[l][r];
    if(r <= 2*l) return dp[l][r] = 0;
    return dp[l][r] = min(Dp(l+1,r)+c[l],Dp(l,r-1)+c[r]);
}

int main(){
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
    int n;
    while(cin >> n){
        memset(c,0,sizeof(c));
        memset(dp,-1,sizeof(dp));
        int Min = maxn,Max = -1;
        for(int i = 0;i < n;i++){
            int tem;
            cin >> tem;
            c[tem]++;
            Min = min(Min,tem);
            Max = max(Max,tem);
        }
        cout << Dp(Min,Max) << endl;;
    }
    return 0;
}


### 关于 Codeforces CF994 Div. 2 的题目与解答 #### 题目概述 Codeforces Round #412 (Div. 2),即 CF994,采用动态评分机制。这种机制意味着一个问题的最大分值取决于解决问题的人数与总参赛人数的比例[^1]。 #### 动态评分机制解释 对于该轮比赛而言,如果某道题目的解决者数量占总参与者的比例较低,则这道题目的分数会相对较高;反之则低。所有至少提交了一次代码的人都被视为参加了这场比赛。 #### 示例解法展示 考虑到不同的算法挑战,在这里提供一道关于字符串处理的问题及其解决方案作为例子: ##### 不同字符计数问题 给定一个长度不超过 \(10^5\) 的字符串,目标是计算其中不同字符的数量并输出重复字符的次数。以下是实现这一功能的一个 C++ 程序片段: ```cpp #include<bits/stdc++.h> using namespace std; const int N=100000+10; char a[N]; int main(){ int n; while(~scanf("%d",&n)){ scanf("%s",a); sort(a,a+n); int x=unique(a,a+n)-a; // 计算不重复字符数目 if(n>26) printf("-1\n"); else printf("%d\n",n-x); // 输出重复字符个数 } return 0; } ``` 此程序通过 `sort` 函数对输入字符串进行了排序,并利用 STL 中的 `unique()` 来去除相邻相同的元素,从而统计出独一无二的字符数量[^2]。 #### 构建三维结构体模型 另一个有趣的案例涉及构建由立方体组成的二维网格表示的物体。每个位置上的整数值代表堆叠在此处的小方块的高度。为了重建这个对象的外观视角下的形态,可以按照如下方法操作: ```cpp #include<bits/stdc++.h> using namespace std; const int N=107; int n,m,h,mp[N][N],a[N],b[N],i,j,k; int main(){ for(scanf("%d%d%d",&n,&m,&h),i=1;i<=m;++i){ scanf("%d",a+i); } for(i=1;i<=n;++i){ scanf("%d",b+i); } for(i=1;i<=n;++i){ for(j=1;j<=m;++j){ scanf("%d",&mp[i][j]); if(mp[i][j]){ mp[i][j]=min(a[j],b[i]); // 取主视图和侧视图高度较小者 } } } for(i=1;i<=n;++i,puts("")){ for(j=1;j<=m;++j){ printf("%d ",mp[i][j]); } } } ``` 这段代码接收了两组数据——分别对应每一列以及每一行的最大可能高度限制,并据此调整实际放置的立方体高度以满足视觉效果的要求[^4]。
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