Example solution for the following challenge: Given input N, print a centered tree, of height N, where the width of the tree expands (+1) in both directions until line N. On line N+1, print out a single centered character, which shall serve as the stump of the tree. edit: simplified the code a little edit2: allowed \n on last line (there was rea…

christmas_tree.c

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

int main(int argc, char *argv[]) {
	if (argc < 2) return -1; 
	int n = atoi(argv[1]), i, l=0, c;
	for (i=1; l<=n; l++,i=l%n+1)
		for (c=1; c<n+i; c++)
			printf("%s%s", c>n-i?"*":" ", c==n+i-1?"\n":"");
	return 0;
}

(Markdown not supported in gist descriptions as of writing this.)
Ex:

$ ./christmas_tree 4
   *   
  ***  
 ***** 
*******
   *