623 - 500!

UVa網站題目連結
My Solved Problems Performance

In these days you can more and more often happen to see programs which perform some useful calculations being executed rather then trivial screen savers. Some of them check the system message queue and in case of finding it empty (for examples somebody is editing a file and stays idle for some time) execute its own algorithm.

As an examples we can give programs which calculate primary numbers.

One can also imagine a program which calculates a factorial of given numbers. In this case it is the time complexity of order O(n) which makes troubles, but the memory requirements. Considering the fact that 500! gives 1135-digit number no standard, neither integer nor floating, data type is applicable here.

Your task is to write a programs which calculates a factorial of a given number.

Assumptions: Value of a number ``n" which factorial should be calculated of does not exceed 1000 (although 500! is the name of the problem, 500! is a small limit).

Input

Any number of lines, each containing value ``n" for which you should provide value of n!

Output

2 lines for each input case. First should contain value ``n" followed by character `!'. The second should contain calculated value n!.

Sample Input

10
30
50
100

Sample Output

10!
3628800
30!
265252859812191058636308480000000
50!
30414093201713378043612608166064768844377641568960512000000000000
100!
9332621544394415268169923885626670049071596826438162146859296389521759999322991
5608941463976156518286253697920827223758251185210916864000000000000000000000000

Solution

  1. import java.io.BufferedInputStream;
  2. import java.math.BigInteger;
  3. import java.util.Scanner;

  4. public class Main {

  5. static int size = 1001;
  6. static Scanner in = new Scanner(new BufferedInputStream(System.in));
  7. static BigInteger[] bigIntArray = new BigInteger[size];
  8. static int input;

  9. public static void main(String[] args) {

  10. bigIntArray[0] = BigInteger.ONE;
  11. bigIntArray[1] = BigInteger.ONE;
  12. for (int i=2; i<size; i++) {
  13. bigIntArray[i] = bigIntArray[i-1].multiply(new BigInteger(String.
  14. valueOf(i)));
  15. }

  16. while (in.hasNext()) {
  17. input = in.nextInt();
  18. System.out.println(input+"!");
  19. System.out.println(bigIntArray[input]);
  20. }
  21. }
  22. }
關鍵字:UVa Online Judge, ACM. Java


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