前序和中序重建二叉樹

輸入某二叉樹的前序遍歷和中序遍歷的結果，請重建出該二叉樹。假設輸入的前序遍歷和中序遍歷的結果中都不含重複的數字。例如輸入前序遍歷序列{1,2,4,7,3,5,6,8}和中序遍歷序列{4,7,2,1,5,3,8,6}，則重建二叉樹並返回。

public class Solution {
    
    public TreeNode reConstructBinaryTree(int [] pre,int [] in) {
        
        return find(pre, in, 0, pre.length - 1, 0, pre.length - 1);
        
    }
    
    public TreeNode find(int [] pre, int [] in, int preStart, int preEnd, int inStart, int inEnd){
        
        if(preStart > preEnd) return null;
        if(preStart == preEnd) return new TreeNode(pre[preStart]);
        TreeNode node = new TreeNode(pre[preStart]);
      
        int rootIndex;
        for(rootIndex = inStart; rootIndex <= inEnd; rootIndex++){
            if(pre[preStart] == in[rootIndex]) break;
        }
       
        int leftLength = rootIndex - inStart, leftPreEnd = preStart + leftLength ;
        node.left = find(pre, in, preStart + 1, leftPreEnd, inStart, rootIndex - 1);
        node.right = find(pre, in, leftPreEnd + 1, preEnd, rootIndex + 1, inEnd);
        return node;
         
    }
}