第十四届蓝桥杯集训——练习解题阶段(无序阶段)-ALGO-150 6-1 递归求二项式系数值

#include <stdio.h>
int C(int k,int n)
{
    if(k==n)
    {
        return 1;
    }
    if(k==0)
    {
        return 1;
    }
    return C(k,n-1)+C(k-1,n-1);
}
int main()
{
    int k,n;
    scanf("%d %d",&k,&n);
    printf("%d",C(k,n));
    return 0;
}

#include <iostream>
using namespace std;
int erxianshi(int k,int n)
{if(k==0||k==n)
	return 1;
	else
	return erxianshi(k,n-1)+erxianshi(k-1,n-1);
	}
int main()
{ int k,n;
	 cin>>k>>n;
	 cout<<erxianshi(k,n);
    system("pause");
    return 0;
}

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
         Scanner sc=new Scanner(System.in);
         String str=sc.nextLine();
         String []str1=str.split(" ");
 	    int k=Integer.parseInt(str1[0]);
 		int n=Integer.parseInt(str1[1]);
 		sc.close();//不需要时关闭
 		System.out.println(r(k,n));
 	}
 	private static int r(int k, int n) {
 		if (k==0 ||k==n) {
 			return 1;
 		}
 		return  r(k,n-1)+r(k-1,n-1);
 	
	}

}

k,n=map(int,input().split())
if k==0 or n==k:
    print("1")
else:
    sum1=1
    sum2=1
    sum3=1
    for i in range(1,n+1):
        sum1 *= i
    for i in range(1,k+1):
        sum2 *= i
    for i in range(1,n-k+1):
        sum3 *= i
    print(sum1//(sum2*sum3))