重建二叉树

二叉树重构算法解析

最新推荐文章于 2025-03-31 21:54:50 发布

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最新推荐文章于 2025-03-31 21:54:50 发布

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本文深入探讨了如何使用前序遍历和中序遍历序列重构二叉树的算法。通过递归方法，详细解释了如何定位根节点，并以此为基准划分左子树和右子树，最终实现完整二叉树的重建。

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */


class Solution {
public:
    TreeNode* reConstructBinaryTree(vector<int> pre,vector<int> vin)
	{
		int length_pre = pre.size();
		int length_vin = vin.size();
		if(length_pre <= 0 || length_vin <= 0 || length_pre != length_vin)
			return NULL;
		TreeNode * root = ConstructBinaryTree(pre, 0, length_pre -1, vin, 0, length_vin - 1);
		return root;
    }
	TreeNode* ConstructBinaryTree(vector<int> pre,int prefirst, int preend, vector<int> vin, int vinfirst, int vinend) 
	{
		if(prefirst > preend || vinfirst > vinend)
			return NULL;
		TreeNode * root = new TreeNode(pre[prefirst]);
		//cout<<root->val<<" ";
		//system("pause");
		int p = -1;
		for(int i = vinfirst; i <= vinend; i++)
		{
			if(vin[i] == pre[prefirst])
			{
				p = i;
				break;
			}
		}
		root->left = ConstructBinaryTree(pre, prefirst + 1, prefirst + p - vinfirst, vin, vinfirst, p - 1);
		//root->right = ConstructBinaryTree(pre, prefirst + p + 1, preend, vin, vinfirst + p + 1, vinend);
		root->right = ConstructBinaryTree(pre, prefirst + (p - vinfirst) + 1, preend, vin,  p + 1, vinend);
		return root;

    }

	
};