HDOJ(HDU) 1570 A C

谙忆

发布于 2021-01-21 15:22:42

2300

发布于 2021-01-21 15:22:42

文章被收录于专栏：程序编程之旅程序编程之旅

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;
    }
}

本文参与腾讯云自媒体同步曝光计划，分享自作者个人站点/博客。

原始发表：2016-04-19 ，如有侵权请联系 cloudcommunity@tencent.com 删除

case