Tree Previous
Execution time limit is 1 second
Runtime memory usage limit is 128 megabytes
Binary search tree is given. Find element previous to the given in a tree.
Definition of a tree:
// Java
class TreeNode
{
public:
int val;
TreeNode left, right, parent;
TreeNode(int x, TreeNode prev) {
val = x;
left = NULL;
right = NULL;
parent = prev;
};
// C++
class TreeNode
{
public:
int val;
TreeNode *left, *right, *parent;
TreeNode(int x, TreeNode *prev = NULL) : val(x), left(NULL), right(NULL), parent(prev) {}
};
Implement function Prev that returns pointer to the previous element in a tree. If previous element does not exist, return NULL.
// Java TreeNode Prev(TreeNode tree)
// C++ TreeNode* Prev(TreeNode *tree)
Example
Function Prev with tree pointing to 12 returns pointer to the node with value 9.
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