HDOJ1570 A C（打表）

A C

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 5704    Accepted Submission(s): 3711

Problem Description

Are you excited when you see the title "AC" ? If the answer is YES , AC it ;

You must learn these two combination formulas in the school . If you have forgotten it , see the picture.

Now I will give you n and m , and your task is to calculate the answer .

Input

In the first line , there is a integer T indicates the number of test cases.
Then T cases follows in the T lines.
Each case contains a character 'A' or 'C', two integers represent n and m. (1<=n,m<=10)

Output

For each case , if the character is 'A' , calculate A(m,n),and if the character is 'C' , calculate C(m,n).
And print the answer in a single line.

Sample Input

2 A 10 10 C 4 2

Sample Output

3628800 6

根据题目给出的公式可以知道都需要1~10的阶乘，可以打表，根据公式计算就OK

import java.util.Scanner;

public class Main{
  private static Scanner scanner;
  private static long arr[];
  public static void main(String[] args) {
    dabiao();
    scanner = new Scanner(System.in);
    int cases = scanner.nextInt();
    while(cases-->0){
      String string = scanner.next();
      int n = scanner.nextInt();
      int m = scanner.nextInt();
      if(string.equals("A")){
        System.out.println(arr[n]/arr[n-m]);
      }else {
        System.out.println(arr[n]/(arr[m]*arr[n-m]));
      }
    }
  }
  private static void dabiao() {
    arr = new long[11];
    arr[0] = 1;
    arr[1] = 1;
    for (int i = 2; i < arr.length; i++) {
      arr[i] = arr[i-1]*i;
    }
  }
}