重建二叉树 java

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重建二叉树 java

题目描述
输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。

代码1：

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode reConstructBinaryTree(int [] pre,int [] in) {
        TreeNode tree = reConstructBinaryTree(pre, 0, pre.length - 1, in, 0, in.length - 1);
        return tree;
    }
    
    private TreeNode reConstructBinaryTree(int[] pre, int preStart, int preEnd, int[] in, int inStart, int inEnd){
        if(preStart > preEnd || inStart > inEnd){
            return null;
        }
        TreeNode root = new TreeNode(pre[preStart]);
        for(int i = inStart; i <= inEnd; i++){
            if(in[i] == pre[preStart]){
                root.left = reConstructBinaryTree(pre, preStart + 1, preStart + i - inStart, in, inStart, i - 1);
                root.right = reConstructBinaryTree(pre, preStart + i - inStart + 1, preEnd, in, i + 1, inEnd);
            }
        }
        return root;
    }
}

代码2：后续有好的想法，在进行补充