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POJ3111 K Best —— 01分数规划 二分法

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题目链接:http://poj.org/problem?id=3111

 

K Best
Time Limit: 8000MS   Memory Limit: 65536K
Total Submissions: 11380   Accepted: 2935
Case Time Limit: 2000MS   Special Judge

Description

Demy has n jewels. Each of her jewels has some value vi and weight wi.

Since her husband John got broke after recent financial crises, Demy has decided to sell some jewels. She has decided that she would keep k best jewels for herself. She decided to keep such jewels that their specific value is as large as possible. That is, denote the specific value of some set of jewels S = {i1i2, …, ik} as

技术分享.

Demy would like to select such k jewels that their specific value is maximal possible. Help her to do so.

Input

The first line of the input file contains n — the number of jewels Demy got, and k — the number of jewels she would like to keep (1 ≤ k ≤ n ≤ 100 000).

The following n lines contain two integer numbers each — vi and wi (0 ≤ vi ≤ 106, 1 ≤ wi ≤ 106, both the sum of all vi and the sum of all wi do not exceed 107).

Output

Output k numbers — the numbers of jewels Demy must keep. If there are several solutions, output any one.

Sample Input

3 2
1 1
1 2
1 3

Sample Output

1 2

Source

Northeastern Europe 2005, Northern Subregion
 
 
 
 
题解:
 
 
 
代码如下:
技术分享
 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <vector>
 7 #include <queue>
 8 #include <stack>
 9 #include <map>
10 #include <string>
11 #include <set>
12 #define ms(a,b) memset((a),(b),sizeof((a)))
13 using namespace std;
14 typedef long long LL;
15 const double EPS = 1e-8;
16 const int INF = 2e9;
17 const LL LNF = 2e18;
18 const int MAXN = 1e5+10;
19 
20 struct node
21 {
22     double d;
23     int a, b, id;
24     bool operator<(const node x)const{
25         return d>x.d;
26     }
27 }q[MAXN];
28 
29 int n, k;
30 
31 bool test(double L)
32 {
33     for(int i = 1; i<=n; i++)
34         q[i].d = 1.0*q[i].a - L*q[i].b;
35 
36     sort(q+1, q+1+n);
37     double sum = 0;
38     for(int i = 1; i<=k; i++)
39         sum += q[i].d;
40     return sum>0;
41 }
42 
43 int main()
44 {
45     while(scanf("%d%d", &n, &k)!=EOF)
46     {
47         for(int i = 1; i<=n; i++)
48         {
49             scanf("%d%d", &q[i].a, &q[i].b);
50             q[i].id = i;
51         }
52 
53         double l = 0, r = 1e7;
54         while(l+EPS<=r)
55         {
56             double mid = (l+r)/2;
57             if(test(mid))
58                 l = mid + EPS;
59             else
60                 r = mid - EPS;
61         }
62 
63         for(int i = 1; i<=k; i++)
64             printf("%d ", q[i].id);
65         printf("\n");
66     }
67 }
View Code

 

 

POJ3111 K Best —— 01分数规划 二分法

标签:desc   pen   accept   arc   strong   for   scan   long   org   

原文地址:http://www.cnblogs.com/DOLFAMINGO/p/7571434.html

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