给出前序中序还原二叉树

/*
给出前序中序还原二叉树，并写出后序遍历

前序遍历： ACFGBDE

中序遍历： FCGADBE

/

/*
A
C B
F G D E


后序遍历： FGCDEBA
/

var qian = [‘a’, ‘c’, ‘f’, ‘g’, ‘b’, ‘d’, ‘e’];
var zhong = [‘f’, ‘c’, ‘g’, ‘a’, ‘d’, ‘b’, ‘e’];

function Node(value) {
this.value = value;
this.left = null;
this.right = null;
}

function f1(qian, zhong) {
if(qian == null || zhong == null || qian.length == 0 || zhong.length == 0 || qian.length != zhong.length) return null;

var root = new Node(qian[0]);<br />    var index = zhong.indexOf(root.value); // 找到根节点在中序遍历中的位置<br />    var qianLeft = qian.slice(1,index+1); //前序遍历的左子树<br />    var qianRight = qian.slice(1 + index, qian.length); //前序遍历的右子树
var zhongLeft = zhong.slice(0, index);//中序遍历的左子树<br />    var zhongRight = zhong.slice(index + 1, zhong.length);//中序遍历的右子树<br />    root.left = f1(qianLeft, zhongLeft);//根据左子树的前序和中序还原左子树并赋值给root.left<br />    root.right = f1(qianRight, zhongRight);//根据右子树的前序和中序还原右子树并赋值给root.right<br />    return root;<br />}   

var root = f1(qian,zhong);

console.log(root.left);
console.log(root.right);