java面试题--已知先序和中序遍历求后序遍历

class Node {public int data;public Node left;public Node right;public Node() {}public Node(int data) {this.data = data;this.left=null;this.left=null;}}public class BinaryTree {private Node root;public BinaryTree() {root=null;}//后序遍历实现public void postOrder(Node localRoot){if(localRoot!=null){postOrder(localRoot.left);postOrder(localRoot.right);System.out.print(localRoot.data+" ");}}public void postOrder(){this.postOrder(this.root);}public void initTree(int[] preOrder,int []inOrder){this.root=this.initTree(preOrder, 0,preOrder.length-1,inOrder,0,inOrder.length);}public Node initTree(int[] preOrder, int start1, int end1, int[] inOrder, int start2,int end2) {if(start1>end1 || start2>end2){return null;}int rootData=preOrder[start1];Node head=new Node(rootData);//根节点所在的位置int rootIndex=findIndexInArray(inOrder,rootData,start2,end2);int offSet=rootIndex-start2-1;//左子树个数//构建左子树head.left=initTree(preOrder,start1+1,start1+1+offSet,inOrder,start2,start2+offSet);//构建右子树head.right=initTree(preOrder,start1+2+offSet,end1,inOrder,rootIndex+1,end2);return head;}public int findIndexInArray(int[] inOrder, int rootData, int begin,int end) {for (int i = begin; i <= end; i++) {if(inOrder[i]==rootData){return i;}}return -1;}public static void main(String[] args) {BinaryTree bt=new BinaryTree();int[]preOrder={1,2,4,8,9,5,10,3,6,7};int[]inOrder={8,4,9,2,10,5,1,6,3,7};bt.initTree(preOrder, inOrder);System.out.println("二叉树的后序遍历：");bt.postOrder();}}