Expend (x+y)^n for a given n

expand.c

#include <stdlib.h>
#include <stdio.h>

int combine(int n, int m)
{
	int s1, s2, i; 
	s1=s2=1; 

	for (i = m+1; i<=n; i++)   s1 *= i;
	for (i = 1; i<=(n-m); i++) s2 *= i; 
	return (s1/s2); 	
}

int main(int argc, char **argv)
{
	int n, i; 

	n = atoi(argv[1]);
	printf("(x+y)^%d = ", n); 
    
    for (i=0; i<=n; i++)
    {
    	int coeff = combine(n, i);
    	if (i != 0) printf(" + "); 
    	printf("%d", coeff); 
    	if (i != n) printf("*x^%d", (n-i)); 
    	if (i != 0) printf("*y^%d", i); 
    }
    printf("\n"); 
    return(0); 
}

expand.rb

def combine(n, m)
	s1 = (m+1..n).inject(1, :*)
	s2 = (1..n-m).inject(1, :*)
	s1/s2
end

def expand(n)
	ret = []
	(0..n).each do |i|
		t1 = ( i == n ) ? '' :  "*x^#{n-i}"
		t2 = ( i == 0 ) ? '' :  "*y^#{i}"
		ret << "#{combine(n, i)}#{t1}#{t2}"  
	end
	"(x+y)^#{n} = #{ret.join(' + ')}"
end

puts expand(ARGV[0].to_i)