Q 102 - Trees - Preorder Traversal

Your task is to implement the following function :

void preorder(TreeNode*)

You will be working with the following structure :

struct TreeNode {
	int x;
    struct TreeNode* L;
    struct TreeNode* R;
}

You may only edit the BODY of the code, leaving the HEAD and the TAIL as it is.

Sample Input 0

7
4 2 1 3 6 7 5

Sample Output 0

4 2 1 3 6 5 7 

Solution :

#include <stdio.h>

#include <stdlib.h>

struct node {

   int data;

   struct node *left;

   struct node *right;

};

struct node *createNode(int val) {

   struct node *temp =  (struct node *)malloc(sizeof(struct node));

   temp->data = val;

   temp->left = temp->right = NULL;

   return temp;

}

void preorder(struct node *root) {

   if (root != NULL) {

      printf("%d ",root->data);

      preorder(root->left);

      preorder(root->right);

   }

}

struct node* insertNode(struct node* node, int val) {   

   if (node == NULL) return createNode(val);

   if (val < node->data)

      node->left  = insertNode(node->left, val);

   else if (val > node->data)

      node->right = insertNode(node->right, val);   

   return node;

}

int main() {

    int val, N; 

    scanf("%d",&N);

   struct node *root = NULL;

   for (int i = 1; i <= N; i++) {

        scanf("%d",&val);

        root = insertNode(root, val);

   }

   preorder(root);

   return 0;

}