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
题意：很简单，看图片就能理解了。
水题一个！就不多解释了。
import java.util.Scanner; public class Main{ public static void main(String[] args) { Scanner sc = new Scanner(System.in); int t = sc.nextInt(); while(t-->0){ String str = sc.next(); int n = sc.nextInt(); int m =sc.nextInt(); if(str.charAt(0)=='A'){ System.out.println(a(n,m)); }else{ System.out.println(c(n,m)); } } } private static int c(int n, int m) { int num =1; if(n-m>m){ m=n-m; } int cnum=1; for(int i=1;i<=n-m;i++){ cnum=cnum*i; } for(int i=m+1;i<=n;i++){ num=num*i; } return num/cnum; } private static int a(int n, int m) { int num=1; for(int i=n-m+1;i<=n;i++){ num=num*i; } return num; } }
