[LeetCode]Construct Binary Tree from Preorder and Inorder Traversal

最新推荐文章于 2024-01-17 14:50:43 发布

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#二叉树

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本文详细介绍了如何通过给定的二叉树的前序和中序遍历序列来构建该二叉树的具体步骤和实现过程。

Given preorder and inorder traversal of a tree, construct the binary tree.

Note:
You may assume that duplicates do not exist in the tree.

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    typedef vector<int>::iterator Ite;
public:
    TreeNode *buildTree(Ite x, Ite y, Ite a, Ite b)
    {
        if (x >= y) return NULL;
        if (y - x == 1) return new TreeNode(*x);
        int i, rv = *x++; // root value
        for (i = 0; i < b - a; i++) if (*(a + i) == rv) break;
        TreeNode *root = new TreeNode(rv);
        root->left = buildTree(x, x + i, a, a + i);
        root->right = buildTree(x + i, y, a + i + 1, b);
        return root;
    }
    TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
        return buildTree(preorder.begin(), preorder.end(), inorder.begin(), inorder.end());
    }
};