poj1064 Cable master

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

 

 

二分答案，做着玩玩。

感觉乘100变成int64搞好一点，我用的double，细节太多，WA无数次。

主要细节是输出的时候不能四舍五入，要直接把小数点后3位之后截掉，因为比如能0.0099，但四舍五入就成了0.01，而实际上是0.00。用int64应该就没有这个问题。

判断函数名一般用什么啊，蒟蒻表示没经验只好用自己喜欢的球星库里了。（要是有有经验的神犇记得留言啊）

program rrr(input,output);
const
  eps=0.000001;
var
  a:array[0..10010]of double;
  n,i:longint;
  k,cnt:int64;
  l,r,mid:double;
function curry(x:double):boolean;
begin
   cnt:=0;
   for i:=1 to n do begin cnt:=cnt+trunc(a[i]/x);if cnt>=k then exit(true); end;
   exit(false);
end;
begin
   assign(input,'r.in');assign(output,'r.out');reset(input);rewrite(output);
   readln(n,k);r:=0;
   for i:=1 to n do begin readln(a[i]);if a[i]>r then r:=a[i]; end;
   l:=0;
   while r-l>eps do
      begin
         mid:=(l+r)/2;
         if curry(mid) then l:=mid else r:=mid;
      end;
   write(trunc(r*100)/100:0:2);
   close(input);close(output);
end.