Here is source code of the C Program to find nth node in the inorder traversal of a tree. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

/*
* C Program to Find Nth Node in the Inorder Traversal of a Tree
*/

typedef struct node
{
int value;
struct node *left;
struct node *right;
}newnode;

newnode *root;
static ctr;

void nthnode(newnode *root, int n, newnode **nthnode);
int main()
{
newnode *temp;
root=0;

// Construct the tree
add(19);
add(20);
add(11);
inorder(root);
// Get the pointer to the nth Inorder node
nthinorder(root, 6, &temp);
printf("\n[%d]\n", temp->value);
return(0);
}

// Get the pointer to the nth inorder node in "nthnode"
void nthinorder(newnode *root, int n, newnode **nthnode)
{
static whichnode;
static found;

if (!found)
{
if (root)
{
nthinorder(root->left, n , nthnode);
if (++whichnode == n)
{
printf("\n Found %dth node\n", n);
found = 1;
*nthnode = root;
}
nthinorder(root->right, n , nthnode);
}
}
}

inorder(newnode *root)
{
}
// Add value to a Binary Search Tree
add(int value)
{
newnode *temp, *prev, *cur;

temp = malloc(sizeof(newnode));
temp->value = value;
temp->left = 0;
temp->right = 0;
if (root == 0)
{
root = temp;
}
else
{
prev = 0;
cur = root;
while(cur)
{
prev = cur;
cur =(value < cur->value)? cur->left : cur->right;
}
if (value > prev->value)
prev->right = temp;
else
prev->left = temp;
}
}


$ cc pgm63.c
$ a.out

[1416572]