JAVA版本：根据二叉树的中序遍历和后序遍历构造出二叉树

根据二叉树的中序遍历和后序遍历构造出二叉树

给出二叉树的中序遍历数组和后序遍历数组构造出该二叉树

二叉树的中序遍历和后序遍历分别为下面的数组：

int[] inorder = {12,15,35,46,57,62,65,68,79};
int[] postorder= {12,35,57,46,15,65,79,68,62};

算法设计如下：

package com.bean.constructbinarytreedemo;

import java.util.ArrayList;
import java.util.Stack;



public class BuildBinaryTreeDemo2 {

    /*
     * 二叉树的前序遍历
     * */
    public static ArrayList preOrder(TreeNode root){
        Stack stack = new Stack();
        ArrayList list = new ArrayList();
        if(root == null){
            return list;
        }
        stack.push(root);
        while(!stack.empty()){
            TreeNode node = stack.pop();
            list.add(node.data);
            if(node.rightChild!=null){
                stack.push(node.rightChild);
            }
            if(node.leftChild != null){
                stack.push(node.leftChild);
            }

        }
        System.out.println(list);
        return list;
    }



    /*
     * 二叉树的中序遍历
     * */
    public static ArrayList inOrder(TreeNode root){
        ArrayList list = new ArrayList();
        Stack stack = new Stack();
        TreeNode current = root;
        while(current != null|| !stack.empty()){
            while(current != null){
                stack.add(current);
                current = current.leftChild;
            }
            current = stack.peek();
            stack.pop();
            list.add(current.data);
            current = current.rightChild;

        }
        System.out.println(list);
        return list;

    }

    /*
     * 二叉树的后续遍历
     * */

    public static ArrayList postOrder(TreeNode root){
        ArrayList list = new ArrayList();
        if(root == null){
            return list;
        }
        list.addAll(postOrder(root.leftChild));
        list.addAll(postOrder(root.rightChild));
        list.add(root.data);
        System.out.println(list);
        return list;
    }


    /*
     * 构造二叉树
     * */
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        return buildBinaryTreeProcess(inorder, postorder, postorder.length - 1, 0, inorder.length - 1);    
      }

    /*
     * 根据二叉树中序遍历和后序遍历的结果构造二叉树
     * */
    public TreeNode buildBinaryTreeProcess(int[] inorder, int[] postorder, int ppos, int is, int ie){
        if(ppos >= postorder.length || is > ie) return null;
        TreeNode node = new TreeNode(postorder[ppos]);
        int pii = 0;
        for(int i = 0; i < inorder.length; i++){
          if(inorder[i] == postorder[ppos]) pii = i;  
        }
        node.leftChild = buildBinaryTreeProcess(inorder, postorder, ppos - 1 - ie + pii, is, pii - 1);
        node.rightChild = buildBinaryTreeProcess(inorder, postorder, ppos - 1 , pii + 1, ie);
        return node;
      }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //int[] preorder = {62,15,12,46,35,57,68,65,79};
        int[] inorder = {12,15,35,46,57,62,65,68,79};
        int[] postorder= {12,35,57,46,15,65,79,68,62};

        BuildBinaryTreeDemo2 buildBT=new BuildBinaryTreeDemo2();
        TreeNode tree = buildBT.buildTree(inorder, postorder);

        buildBT.preOrder(tree);
        buildBT.inOrder(tree);
        buildBT.postOrder(tree);


    }

}

（完）