@@ -622,7 +622,42 @@ class Solution {
622622 }
623623}
624624```
625+ ``` java
626+ class Solution {
627+ public TreeNode buildTree (int [] inorder , int [] postorder ) {
628+ if (postorder. length == 0 || inorder. length == 0 )
629+ return null ;
630+ return buildHelper(inorder, 0 , inorder. length, postorder, 0 , postorder. length);
631+ 632+ }
633+ private TreeNode buildHelper (int [] inorder , int inorderStart , int inorderEnd , int [] postorder , int postorderStart , int postorderEnd ){
634+ if (postorderStart == postorderEnd)
635+ return null ;
636+ int rootVal = postorder[postorderEnd - 1 ];
637+ TreeNode root = new TreeNode (rootVal);
638+ int middleIndex;
639+ for (middleIndex = inorderStart; middleIndex < inorderEnd; middleIndex++ ){
640+ if (inorder[middleIndex] == rootVal)
641+ break ;
642+ }
625643
644+ int leftInorderStart = inorderStart;
645+ int leftInorderEnd = middleIndex;
646+ int rightInorderStart = middleIndex + 1 ;
647+ int rightInorderEnd = inorderEnd;
648+ 649+ 650+ int leftPostorderStart = postorderStart;
651+ int leftPostorderEnd = postorderStart + (middleIndex - inorderStart);
652+ int rightPostorderStart = leftPostorderEnd;
653+ int rightPostorderEnd = postorderEnd - 1 ;
654+ root. left = buildHelper(inorder, leftInorderStart, leftInorderEnd, postorder, leftPostorderStart, leftPostorderEnd);
655+ root. right = buildHelper(inorder, rightInorderStart, rightInorderEnd, postorder, rightPostorderStart, rightPostorderEnd);
656+ 657+ return root;
658+ }
659+ }
660+ ```
626661105.从前序与中序遍历序列构造二叉树
627662
628663``` java
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