POJ 1064 - Cable master(二分)

Cable master
Time Limit: 1000MS Memory Limit: 10000K
Total Submissions: 37699 Accepted: 8021
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,要求剪成m条长度相同的线段.要使得这m条线段尽可能的长.单位长度是米,要求精确到小数点后两位(厘米).

解题思路:
对m条线段的长度进行二分,找出最大值.同时让数值乘以100,使得单位长度为厘米,方便运算.

用cnt记录对于m线段的最大长度所能截得的个数,如果cnt小于m,说明长度过大,如果cnt大于等于m,那么继续找m的最大值.

AC代码

#include<stdio.h>#include<algorithm>#define maxn 10005using namespace std;int qdu[maxn];int main(){    int n;    int m;    while(~scanf("%d%d",&n,&m))    {        double tmp;        int MAX = 0;        for(int i = 0;i < n;i++)        {            scanf("%lf",&tmp);            qdu[i] = tmp*100;            MAX = max(MAX,qdu[i]);        }        int low = 1;        int high = MAX;        int res = 0;        while(low <= high)        {            int mid = (low + high) >> 1;            int cnt = 0;            for(int i = 0;i < n;i++)    cnt += qdu[i] / mid;            if(cnt < m) high = mid-1;            else    low = mid+1,res = max(res,mid);        }        printf("%.2f\n",(double)(res/100.0));    }    return 0;}