POJ 1064 Cable master (二分 分數化整數)

 

Cable master Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 28764   Accepted: 6091

 

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

Source

Northeastern Europe 2001

 

題目大意：有n根繩子，每根長用一個精度為0.01的實數表示，現在要把全部分成等長的k份，問每份最長是多少

題目分析：典型的二分題，可以直接二分小數，但是不推薦這樣，二分小數有很多細節不好處理，直接.2f好像會自動四捨五入，因為題目給的都是保留兩位的，直接乘100轉換成整數二分，最後輸出的時候除100.0，這樣貌似就不會四捨五入了。

#include 
#include 
using namespace std;
int a[10005];
int n, k;

bool ok(int m)
{
	int cnt = 0;
    for(int i = 0; i < n; i++)
        cnt += a[i] / m;
    return cnt >= k;
}

int main()
{
    while(scanf(%d %d, &n, &k) != EOF)
    {
        int ma = 0;
        for(int i = 0; i < n; i++)
        {
        	double tmp;
            scanf(%lf, &tmp);
            a[i] = (int)(tmp * 100);
            ma = max(ma, a[i]);
        }
        int r = ma, l = 1;
        while(l <= r)
        {
            int mid = (l + r) / 2;
            if(ok(mid)) 
            	l = mid + 1;
            else
                r = mid - 1;
        }
        //注意這裡答案是r不是l，因為cnt比k小是符合條件的，大於k就不符合條件了
        printf(%.2f
, (double)r / 100.0);
    }
}