[leetcode]Construct Binary Tree from Inorder and Postorder Traversal

Construct Binary Tree from Inorder and Postorder Traversal

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

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

算法：很基础。跟[leetcode]Construct Binary Tree from Preorder and Inorder Traversal类似，根据中序序列和后序序列构建二叉树。

public class Solution {
    public TreeNode buildTree(int[] inorder, int[] postorder) {
         if(inorder == null || postorder == null || inorder.length != postorder.length || inorder.length == 0) return null;
         int length = inorder.length ;
         int val = postorder[length - 1];
         int mid = 0;
         for(int i = 0; i < length; i++){
             if(val == inorder[i]){
                 mid = i;
                 break;
             }
         }
         int[] leftInorder = Arrays.copyOfRange(inorder, 0, mid);
         int[] leftPost = Arrays.copyOfRange(postorder, 0, mid);
         int[] rightInorder = Arrays.copyOfRange(inorder, mid + 1, length);
         int[] rightPost = Arrays.copyOfRange(postorder, mid, length - 1);
         TreeNode root = new TreeNode(val);
         root.left = buildTree(leftInorder,leftPost);
         root.right = buildTree(rightInorder, rightPost);
         return root;
     
    }
}