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99-recover-binary-search-tree.cpp
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99-recover-binary-search-tree.cpp
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/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
TreeNode* firstMistake, *secondMistake, *prev;
void recoverTree(TreeNode* root) {
prev = new TreeNode(INT_MIN);
inorder(root);
swap(firstMistake->val, secondMistake->val);
}
void inorder(TreeNode* root) {
// null ptr check
if(root == nullptr)
return;
inorder(root->left);
if(firstMistake == nullptr && root->val < prev->val) // if 1st mistake is not yet marked
firstMistake = prev;
if(firstMistake != nullptr && root->val < prev->val) // if 1st mistake isSet already
secondMistake = root;
prev = root;
inorder(root->right);
}
};