java-从先序遍历和中序遍历创建二叉树

public class BuildTreePreOrderInOrder {/** * Build Binary Tree from PreOrder and InOrder *  _______7______       /              \    __10__          ___2   /      \        /   4       3      _8            \    /             1  11              */public static void main(String[] args) {BuildTreePreOrderInOrder build=new BuildTreePreOrderInOrder();int[] preOrder = {7,10,4,3,1,2,8,11};int[] inOrder = {4,10,3,1,7,11,8,2};Node root=build.buildTreePreOrderInOrder(preOrder,0,preOrder.length-1,inOrder,0,preOrder.length-1);build.preOrder(root);System.out.println();build.inOrder(root);}public Node buildTreePreOrderInOrder(int[] preOrder,int begin1,int end1,int[] inOrder,int begin2,int end2){if(begin1>end1||begin2>end2){return null;}int rootData=preOrder[begin1];Node head=new Node(rootData);int divider=findIndexInArray(inOrder,rootData,begin2,end2);int offSet=divider-begin2-1;Node left=buildTreePreOrderInOrder(preOrder,begin1+1,begin1+1+offSet,inOrder,begin2,begin2+offSet);Node right=buildTreePreOrderInOrder(preOrder,begin1+offSet+2,end1,inOrder,divider+1,end2);head.left=left;head.right=right;return head;}public int findIndexInArray(int[] a,int x,int begin,int end){for(int i=begin;i<=end;i++){if(a[i]==x)return i;}return -1;}public void preOrder(Node n){if(n!=null){System.out.print(n.val+",");preOrder(n.left);preOrder(n.right);}}public void inOrder(Node n){if(n!=null){inOrder(n.left);System.out.print(n.val+",");inOrder(n.right);}}class Node{Node left;Node right;int val;public Node(int val){this.val=val;}public Node getLeft(){return left;}public Node getRight(){return right;}public int getVal(){return val;}}}