import java.util.*;
public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sca=new Scanner(System.in);
		while(true){
			double ai=sca.nextInt();
			double bi=sca.nextInt();
			if(ai==0&&bi==0){
				break;
			}else{
				double pd=ai/2;
				if(bi<=pd){
					double sum=1;
					double start=ai-bi;
					for(double i=start+1;i<=ai;i++){
						sum=sum*i;
					}
					long sum2=1;
					for(long i=2;i<=bi;i++){
						sum2=sum2*i;
					}System.out.println(String.format("%.0f", sum/sum2));
					
				}else{
					double sum=1;
					double start=ai-bi;
					for(double i=bi+1;i<=ai;i++){
						sum=sum*i;
					}
					double sum2=1;
					for(double i=1;i<=start;i++){
						sum2=sum2*i;
					}System.out.println(String.format("%.0f", sum/sum2));
				}
				
			}
		}
	
	}	

}

• Re:大家可以用概率的阶乘公式来过，不过要用double，不然wa，符Ac java代码，注，double表示的数比long的大 (566) forif 2014-03-16 12:01:30