Problem Statment: Given a binary tree, find if there exists a root to leaf path of distance k.

 /*Level : Easy question */  
 #include <stdio.h>  
 #include <stdlib.h>  
 /* A binary tree node has data, pointer to left child  
   and a pointer to right child */  
 struct node  
 {  
   int data;  
   struct node* left;  
   struct node* right;  
 };  
 /* Helper function to create a new node */  
 struct node* newNode(int data)  
 {  
   struct node* node = (struct node*)  
                malloc(sizeof(struct node));  
   node->data = data;  
   node->left = NULL;  
   node->right = NULL;  
   return(node);  
 }  
 /*Utility function to determine path from root to leaf with given distance exists or not*/  
 int kdistance(struct node *root , int dist)  
 {  
  if(!root)  
  return 0;  
  if(dist==0 && root->left == NULL && root->right == NULL)  
  {  
  printf("leaf reached when k = 0 is %d\n",root->data);  
  return 1;  
  }  
  else  
  {  
  (--dist);  
  return (kdistance(root->left,dist)) || (kdistance(root->right,dist)) ;  
  }  
 }  
 /* Driver program*/  
 int main()  
 {  
   struct node *root1 = newNode(1);  
   root1->left = newNode(2);  
   root1->right = newNode(3);  
   root1->left->left = newNode(4);  
   root1->left->right = newNode(5);  
   root1->right->left = newNode(6);  
   root1->right->right = newNode(7);  
  int k=2;  
  if(kdistance(root1,k))  
     printf("Path exists for k = %d\n",k);  
    else  
  printf("Path does not exist for k = %d\n",k);  
   getchar();  
  return 0;  
 }