[Leetcode] Construct binary tree from inorder and postorder Traversal

Source: Internet
Author: User

Construct binary tree from inorder and postorder Traversal

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

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

Algorithm: very basic. Similar to [leetcode] Construct binary tree from preorder and inorder traversal, a binary tree is constructed based on the central sequence and the post sequence.

 1 public class Solution { 2     public TreeNode buildTree(int[] inorder, int[] postorder) { 3          if(inorder == null || postorder == null || inorder.length != postorder.length || inorder.length == 0) return null; 4          int length = inorder.length ; 5          int val = postorder[length - 1]; 6          int mid = 0; 7          for(int i = 0; i < length; i++){ 8              if(val == inorder[i]){ 9                  mid = i;10                  break;11              }12          }13          int[] leftInorder = Arrays.copyOfRange(inorder, 0, mid);14          int[] leftPost = Arrays.copyOfRange(postorder, 0, mid);15          int[] rightInorder = Arrays.copyOfRange(inorder, mid + 1, length);16          int[] rightPost = Arrays.copyOfRange(postorder, mid, length - 1);17          TreeNode root = new TreeNode(val);18          root.left = buildTree(leftInorder,leftPost);19          root.right = buildTree(rightInorder, rightPost);20          return root;21      22     }23 }


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