36 lines
1.3 KiB
C++
36 lines
1.3 KiB
C++
#include <vector>
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#include <algorithm>
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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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* 105. Construct Binary Tree from Preorder and Inorder Traversal
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* Given two integer arrays preorder and inorder where preorder is the preorder traversal of a binary tree and inorder is the inorder traversal of the same tree, construct and return the binary tree.
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*/
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class Solution {
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private:
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TreeNode* buildTree(std::vector<int>::const_iterator preBegin, std::vector<int>::const_iterator preEnd, std::vector<int>::const_iterator inBegin, std::vector<int>::const_iterator inEnd) {
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if (preBegin == preEnd)
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return nullptr;
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if (std::next(preBegin) == preEnd)
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return new TreeNode(*preBegin);
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auto midIt = std::find(inBegin, inEnd, *preBegin);
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auto lenL = std::distance(inBegin, midIt);
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return new TreeNode(
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*preBegin,
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buildTree(preBegin + 1, preBegin + 1 + lenL, inBegin, midIt),
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buildTree(preBegin + 1 + lenL, preEnd, midIt + 1, inEnd)
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);
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}
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public:
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TreeNode* buildTree(const std::vector<int>& preorder, const std::vector<int>& inorder) {
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return buildTree(preorder.begin(), preorder.end(), inorder.begin(), inorder.end());
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}
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}; |