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Construct Binary Tree from Preorder and Inorder Traversal

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Description

https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/description/

Solution

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
        if (preorder.size() == 0) return NULL;
        return this->build(preorder, inorder, 0, inorder.size() - 1, 0, preorder.size() - 1);
    }
    
    TreeNode* build(vector<int>& preorder, vector<int>& inorder, int inLeft, int inRight, int preLeft, int preRight) {
        if (inLeft > inRight || preLeft > preRight) return NULL;
        TreeNode* root = new TreeNode(preorder[preLeft]);
        int preIndex = preLeft;
        int inIndex = inLeft;
        while (inIndex <= inRight) {
            if (inorder[inIndex] == preorder[preLeft]) {
                break;
            }
            preIndex += 1;
            inIndex += 1;
        }
        root->left = this->build(preorder, inorder, inLeft, inIndex - 1, preLeft + 1, preIndex);
        root->right = this->build(preorder, inorder, inIndex + 1, inRight, preIndex + 1, preRight);
        return root;
    }
};