LeetCode 刷题【106. 从中序与后序遍历序列构造二叉树】

106. 从中序与后序遍历序列构造二叉树

自己做

解：后序遍历

/*** Definition for a binary tree node.* public class TreeNode {*     int val;*     TreeNode left;*     TreeNode right;*     TreeNode() {}*     TreeNode(int val) { this.val = val; }*     TreeNode(int val, TreeNode left, TreeNode right) {*         this.val = val;*         this.left = left;*         this.right = right;*     }* }*/
class Solution {private Map<Integer, Integer> m = new HashMap<Integer, Integer>();private int index;public TreeNode postTravel(int[] inorder, int[] postorder, int begin, int end){if(begin > end)return null;int mid =  m.get(postorder[index]);                               //分割点TreeNode root = new TreeNode(postorder[index--]);                 //中TreeNode right = postTravel(inorder, postorder, mid + 1, end);    //右TreeNode left = postTravel(inorder, postorder, begin, mid - 1);   //左root.right = right;root.left = left;return root;}public TreeNode buildTree(int[] inorder, int[] postorder) {index = inorder.length - 1;for(int i = 0; i < inorder.length; i++)m.put(inorder[i], i);return postTravel(inorder, postorder, 0, inorder.length - 1);}
}