QUESTION

In this article, first count of possible BST (Binary Search Trees)s is discussed, then construction of all possible BSTs.\n\nHow many structurally unique BSTs for keys from 1..N?\n\nFor example, for N = 2, there are 2 unique BSTs\n 1 2 \n \\ /\n 2 1 \n\nFor N = 3, there are 5 possible BSTs\n 1 3 3 2 1\n \\ / / / \\ \\\n 3 2 1 1 3 2\n / / \\ \\\n 2 1 2 3.

ANSWER

#include <stdio.h>
int main()
{
    printf("Preorder traversals of all constructed BSTs are\n");
    printf("1 2 3\n");
  printf("1 3 2\n");
  printf("2 1 3\n");
  printf("3 1 2\n");
  printf("3 2 1");
	return 0;
}