Cable master
Time Limit: 1000MS Memory Limit: 10000K
Total Submissions: 43004 Accepted: 9209
Description
Inhabitants of the Wonderland have decided to hold a regional programming contest. The Judging Committee has volunteered and has promised to organize the most honest contest ever. It was decided to connect computers for the contestants using a “star” topology - i.e. connect them all to a single central hub. To organize a truly honest contest, the Head of the Judging Committee has decreed to place all contestants evenly around the hub on an equal distance from it.
To buy network cables, the Judging Committee has contacted a local network solutions provider with a request to sell for them a specified number of cables with equal lengths. The Judging Committee wants the cables to be as long as possible to sit contestants as far from each other as possible.
The Cable Master of the company was assigned to the task. He knows the length of each cable in the stock up to a centimeter,and he can cut them with a centimeter precision being told the length of the pieces he must cut. However, this time, the length is not known and the Cable Master is completely puzzled.
You are to help the Cable Master, by writing a program that will determine the maximal possible length of a cable piece that can be cut from the cables in the stock, to get the specified number of pieces.
Input
The first line of the input file contains two integer numb ers N and K, separated by a space. N (1 = N = 10000) is the number of cables in the stock, and K (1 = K = 10000) is the number of requested pieces. The first line is followed by N lines with one number per line, that specify the length of each cable in the stock in meters. All cables are at least 1 meter and at most 100 kilometers in length. All lengths in the input file are written with a centimeter precision, with exactly two digits after a decimal point.
Output
Write to the output file the maximal length (in meters) of the pieces that Cable Master may cut from the cables in the stock to get the requested number of pieces. The number must be written with a centimeter precision, with exactly two digits after a decimal point.
If it is not possible to cut the requested number of pieces each one being at least one centimeter long, then the output file must contain the single number “0.00” (without quotes).
Sample Input
4 11
8.02
7.43
4.57
5.39
Sample Output
2.00
题意：给出n条线段，截取成k段，要求段长最长，如果筹不够m条，输出0.00；线段以米的单位给出，小数点位精确到厘米，且段长不能小于1厘米。
做法:二分；
第一点：长度上限应该max{a[i]}.另外根据题目要求最短不能小于1.
第二点：当cou >= k时，继续到右半区间二分；
否则去左半区间二分
#include<stdio.h>
#include<math.h>
#include<string.h>
#include<stdlib.h>
#include<iostream>
#include<algorithm>
using namespace std;
#include<map>
#include<queue>
#include<vector>
const int N=10010;
int a[N];
int main()
{
int n,k;
double len;
while(scanf("%d%d",&n,&k)!=EOF)
{
int maxn=0;
for(int i=0; i<n; i++)
{
scanf("%lf",&len);
a[i]=len*100;//化成厘米的形式
maxn= max(maxn,a[i]);//长度上限
}
int l=1,r=maxn;//题目要求长度不能小于1，所以左极限是1
int res=0;//存储最大的段长
while(l<=r)
{
int mid=(l+r)/2;
int cou=0;//段数量
for(int i=0; i<n; i++)
cou += a[i] / mid;
if(cou >= k)//段数大于所需段数
res = max(res, mid),l = mid + 1;//向右找到一个更大的段长
else
r=mid-1;//否则向左查找
}
printf("%.2lf
",(double)res / 100.0);
}
return 0;
}