Display a line of Pascals Triangle

pascal.c

/*
 * Pascals Triangle in C
 *
 * Hacker News: http://news.ycombinator.com/item?id=3428984
 *
 */

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

long * next_line( long *line, int *length )
{
	(*length)++;
	long *next_line = (long*)malloc(sizeof(long)* *length);
	int p=0;
	for (; p<*length; ++p) {
		if (p==0 || p==(*length)-1) {
			next_line[p] = 1;
		} else {
			next_line[p] = line[p-1] + line[p];
		}
	}
	free(line);
	return next_line;
}

int main( int argc, char **argv )
{
	if (argc!=2) {
		printf("Usage:\n\t%s <n>\nDisplay nth line of Pascal's triangle.\n",argv[0]);
		exit(1);
	}
	long *line = NULL;
	int length = 0;
	int n = atoi(argv[1]);
	int i=0;
	for (; i<n; ++i) {
		line = next_line( line,&length );
	}
	for (i=0; i<length; ++i) {
		printf ("%ld ",line[i]);
	}
	printf("\n");
	return 0;
}