剑指offer面试题6：重建二叉树

public class Solution
{
public TreeNode reConstructBinaryTree(int [] pre,int [] in)
{
TreeNode root=reConstructBinaryTree(pre,0,pre.length-1,in,0,in.length-1);
return root;
}
//前序遍历{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}
private TreeNode reConstructBinaryTree(int [] pre,int startPre,int endPre,int [] in,int startIn,int endIn)
{
if(startPre>endPre||startIn>endIn)
return null;
TreeNode root=new TreeNode(pre[startPre]);

for(int i=startIn;i<=endIn;i++)
if(in[i]==pre[startPre])
{
root.left=reConstructBinaryTree(pre,startPre+1,startPre+i-startIn,in,startIn,i-1);
root.right=reConstructBinaryTree(pre,i-startIn+startPre+1,endPre,in,i+1,endIn);
}

return root;
}
}

public class TreeTest
{
public static String[] str;
public static int count;
/**
* 静态内部类，定义二叉树节点
*/
static class TreeNode
{
public String data;
TreeNode lchild;
TreeNode rchild;
public TreeNode(String x)
{
this.data = x;
}
}
/**
* 根据前序序列递归构建二叉树
*
* @return
*/
public static TreeNode createBtree()
{
TreeNode root = null;
if (count >= str.length || str[count++].equals("#"))
{
root = null;
}
else
{
root = new TreeNode(str[count - 1]);
root.lchild = createBtree();
root.rchild = createBtree();
}
return root;
}
/**
* 前序遍历
*
* @param root
*/
public static void preTraverse(TreeNode root)
{
if (root != null)
{
System.out.print(root.data + " ");
preTraverse(root.lchild);
preTraverse(root.rchild);
}
}
/**
* 中序遍历
*
* @param root
*/
public static void inTraverse(TreeNode root)
{
if (root != null)
{
inTraverse(root.lchild);
System.out.print(root.data + " ");
inTraverse(root.rchild);
}
}
/**
* 后序遍历
*
* @param root
*/
public static void postTraverse(TreeNode root)
{
if (root != null)
{
postTraverse(root.lchild);
postTraverse(root.rchild);
System.out.print(root.data + " ");
}
}

public static void main(String args[])
{
Scanner cin = new Scanner(System.in);
while (cin.hasNext())
{
String s = cin.nextLine();
str = s.split(",");
count = 0;
TreeNode root = createBtree();
// 前序遍历
preTraverse(root);
System.out.println();
// 中序遍历
inTraverse(root);
System.out.println();
// 后序遍历
postTraverse(root);
System.out.println();
}
cin.close();
}
}