36 lines
1.2 KiB
C++
36 lines
1.2 KiB
C++
#include <functional>
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struct TreeNode {
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int val;
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TreeNode* left;
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TreeNode* right;
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explicit TreeNode(int x, TreeNode* left = nullptr, TreeNode* right = nullptr) : val(x), left(left), right(right) {}
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};
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/**
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* 538. Convert BST to Greater Tree
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* Given the root of a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus the sum of all keys greater than the original key in BST.
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* As a reminder, a binary search tree is a tree that satisfies these constraints:
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* The left subtree of a node contains only nodes with keys less than the node's key.
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* The right subtree of a node contains only nodes with keys greater than the node's key.
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* Both the left and right subtrees must also be binary search trees.
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*/
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class Solution {
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public:
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static TreeNode* convertBST(TreeNode* root) {
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if (!root)
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return nullptr;
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int x = 0;
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std::function<void(TreeNode*)> reversedInOrderTraverse = [&](TreeNode* r) {
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if (r->right)
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reversedInOrderTraverse(r->right);
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r->val = (x += r->val);
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if (r->left)
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reversedInOrderTraverse(r->left);
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};
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reversedInOrderTraverse(root);
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return root;
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}
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};
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