重建二叉树06

class Node{int val;Node left;Node right;public Node(int val) {// TODO Auto-generated constructor stubthis.val=val;}}public class MyCreateBinaryTree { staticboolean valid=true;  //是否为有效输入public static void main(String[] args) {// TODO Auto-generated method stubint pre[]={1,2,4,7,3,5,6,8};int in[]={4,7,2,1,5,3,8,6};Node root=recreateBinaryTree(pre,in);if (valid) {display (root);}else {System.out.println("invalid input");}}private static void display(Node root) {// TODO Auto-generated method stubif (root!=null) {System.out.print(root.val+" ");display(root.left);display(root.right);}}private static Node recreateBinaryTree(int[] pre, int[] in) {// TODO Auto-generated method stubNode root=createRecursive(pre,0,pre.length-1,in,0,in.length-1);return root;}private static Node createRecursive(int[] pre, int startPre, int endPre, int[] in, int startIn, int endIn) {// TODO Auto-generated method stubif (pre==null||in==null) {valid=false;return null;}Node root=new Node(pre[startPre]);int rootInorder=startIn;  //在中序遍历中找到根节点的位置while (rootInorder<=endIn&&in[rootInorder]!=root.val) {rootInorder++;}if (rootInorder>endIn) {valid=false;return null;}int leftLength=rootInorder-startIn;if (leftLength>0) {//如果存在左子树root.left=createRecursive(pre,startPre+1,startPre+leftLength,in,startIn,rootInorder-1);}if (leftLength<endPre-startPre) {//如果存在右子树root.right=createRecursive(pre, startPre+leftLength+1, endPre, in, rootInorder+1, endIn);}return root;}}