创建二叉树

给定一棵二叉树的先序遍历和中序遍历，得到该二叉树。

代码：

public class BuildTree {
public static void main(String[] args) {
int[] preorder = {7,10,4,3,1,2,8,11};
int[] inorder = {4,10,3,1,7,11,8,2};

TreeNode root = buildByPreAndIn(preorder, 0, preorder.length-1, inorder, 0, inorder.length-1);

preOrder(root);
System.out.println();
inOrder(root);

}

public static TreeNode buildByPreAndIn(int[] preorder, int begin1, int end1, int[] inorder, int begin2, int end2){
if(begin1 > end1 || begin2 > end2){
return null;
}

int rootdata = preorder[begin1];
TreeNode root = new TreeNode(rootdata);
int rootdataindex = findIndexByOrder(inorder, rootdata, begin2, end2);
int sub = rootdataindex - begin2;
TreeNode left = buildByPreAndIn(preorder, begin1+1, begin1+sub, inorder, begin2, rootdataindex-1);
TreeNode right = buildByPreAndIn(preorder, begin1+sub+1, end1, inorder, rootdataindex+1, end2);
root.left = left;
root.right = right;

return root;
}

public static void preOrder(TreeNode root){
if(root != null){
System.out.print(root.val + " ");
preOrder(root.left);
preOrder(root.right);
}
}

public static void inOrder(TreeNode root){
if(root != null){
inOrder(root.left);
System.out.print(root.val + " ");
inOrder(root.right);
}
}

public static int findIndexByOrder(int[] order, int rootdata, int begin2, int end2){
for(int i=begin2; i<=end2; ++i){
if(order[i] == rootdata){
return i;
}
}
return -1;
}
}




class TreeNode{
int val;
TreeNode left;
TreeNode right;

public TreeNode(int val){
this.val = val;
}
}