import java.util.Scanner;
class a248{
 public static void main(String args[]){
  Scanner scanner = new Scanner(System.in);
  while(scanner.hasNext()){
   int number1 = scanner.nextInt(),number2 = scanner.nextInt(),precise = scanner.nextInt();
   if(precise == 0){
    System.out.println(number1 / number2);
   }else if(number1 % number2 == 0 && precise > 0){
    System.out.print(number1 / number2+".");
    for(int time = 0;time < precise;time++){
     System.out.print("0");
    }
    System.out.println();
   }else{
    System.out.print(number1 / number2+".");
    int remainder = number1 % number2;
    for(int time = 0;time < precise;time++){
     remainder *= 10;
     System.out.print(remainder / number2);
     remainder = remainder % number2;
    }
    System.out.println();
   }
   
  }
 }
}

可以想想看有什麼更快的演算法來優化 :)

可以想想看有什麼更快的演算法來優化 :) 

 System.out.print() 這個方法很慢喔!

可以 在 String 中+=   算完以後再System.out.println();

若是想要更快的話。可以學遺下StringBuffer的用法

StringBuffer比String 快上好幾倍喔!!