C :

#include<stdio.h>

int main()
{
	int t,n,m,i;
	double s1,s2;
	scanf("%d",&t);
	while(t--)
	{
		scanf("%d%d",&n,&m);
		if(n<m)
			printf("0\n");
		else
		{
			for(s1=1,i=n-m+1;i<=n;i++)
				s1*=i;
			for(s2=i=1;i<=m;i++)
				s2*=i;
			printf("%.lf\n",s1/s2);
		}
	}
	return 0;
}

C++ :

#include<stdio.h>

int main()
{
	int t,n,m,i;
	double s1,s2;
	scanf("%d",&t);
	while(t--)
	{
		scanf("%d%d",&n,&m);
		if(n<m)
			printf("0\n");
		else
		{
			for(s1=1,i=n-m+1;i<=n;i++)
				s1*=i;
			for(s2=i=1;i<=m;i++)
				s2*=i;
			printf("%.lf\n",s1/s2);
		}
	}
	return 0;
}

Java :

import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Scanner;
import java.math.*;
public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in = new Scanner(System.in);
		String[] zong = in.nextLine().split(" ");
		int start=Integer.parseInt(zong[0]);
		for(int i=0;i<start;i++){
			String[] nei= in.nextLine().split(" ");
			int[] zh=new int[2];
			zh[0]=Integer.parseInt(nei[0]);
			zh[1]=Integer.parseInt(nei[1]);
			if(zh[0]<zh[1]){System.out.println("0");continue;}
			System.out.println(check(zh[0],zh[1]));
			
		}
			
		
	}


	
private static  BigInteger check(int a, int b) {
		// TODO Auto-generated method stub
	BigInteger c = new BigInteger("0");
		c=jx(a).divide((jx(b).multiply(jx(a-b))));
	return c;
	}



public static int jc(int i){      
    if(i<0)                          //<0退出
       return -1;
    else if(i==0)                     //0的阶乘=1
       return 1;
     else//0继续递归
       return i*jc(i-1);
}
public static BigInteger jx(int i){
	  BigInteger n = new BigInteger("1");
	  BigInteger n1 = new BigInteger("1");
	  for (int j = 1; j <= i; j++) {
	   n1 = n.multiply(BigInteger.valueOf(j));
	   n = n1;
	  }
	return n;

}
}