根據前序遍歷和中序遍歷，利用遞迴的思想實現重建二叉樹，並輸出後序遍歷

程式碼如下：

/**
 * Created by Administrator on 2018/11/28.
 */
class TreeNode{//建立類
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x){
        val=x;
    }
}
public class Solution_1 {
    public static void main(String args[]){
        int[] pre={1,2,4,7,3,5,6,8};
        int[] in={4,7,2,1,5,3,8,6};
        TreeNode tree=reConstructBinaryTree(pre,in);
        System.out.println("後序遍歷結果為：");
        postTraverseBinTree(tree);
    }
    public static TreeNode reConstructBinaryTree(int [] pre,int [] in) {
        TreeNode root=reConstructBinaryTree(pre,0,pre.length-1,in,0,in.length-1);
        return root;
    }
    private static 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);
                break;
            }

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