树的创建以及树的遍历(递归和非递归方法)

//定义树
function TreeNode (value,left,right) {
this.value = value;
this.left = null;
this.right = null;
}
//把数组转化成树
function arrToTree (arr) {
var tree = [];
tree[0] = new TreeNode(arr[0]);//用数组保存结点，之后添加的时候方便查找是哪个结点的子树
for (var i=1; i < arr.length; i++) {
tree[i] = new TreeNode(arr[i]);
if (i % 2 ==1) {
if(arr[i] != '') {
tree[parseInt((i-1)/2)].left = tree[i];//寻找父节点，并判断是左子树还是右子树
}
} else {
if(arr[i] != '') {
tree[parseInt((i-1)/2)].right = tree[i];
}
}
}
return tree[0];
}

//算法1: 前序遍历树
//参数里面放result是一个很好的不会把result每次清空的办法
function preOrder (tree,result) {
if (tree == null) {
return;
}
result.push(tree.value);
preOrder(tree.left,result);
preOrder(tree.right,result);
return result;
}

//算法2: 前序遍历树非递归方法
function preOrder2 (tree) {
var stack = [];
var result = [];
if (tree == null) {
return;
}
stack.push(tree);
while (stack.length > 0) {
var node = stack.pop();
result.push(node.value);
//注意进栈顺序，跟着算法走一遍看看
if(node.right != null) {
stack.push(node.right);
}
if(node.left != null) {
stack.push(node.left);
}
}
return result;
}
//var tree = arrToTree([1,2,3,4,5,'',6,7,8,9,'','','','','',6]);
//console.log(preOrder2(tree));

//算法3: 中序遍历递归方法
function midOrder (tree,result) {
if(tree == null) {
return;
}
midOrder (tree.left,result);
result.push(tree.value);
midOrder (tree.right,result);
return result;
}
//var tree = arrToTree([1,2,3,4,5,'',6,7,8,9,'','','','','','','',10]);
//console.log(midOrder(tree,[]));

//算法4: 中序遍历非递归方法
function midOrder2 (tree) {
var stack = [];
var result = [];
var node = tree;
while (stack.length > 0 || node) {
if (node) {
stack.push(node);
node = node.left;
} else {
var node = stack.pop();
result.push(node.value);
node = node.right;
}
}
return result;
}

//算法5: 后序遍历递归算法
function postOrder(tree,result) {
if (tree == null) {
return;
}
postOrder(tree.left,result);
postOrder(tree.right,result);
result.push(tree.value);
return result;
}

//算法6: 后序遍历非递归算法
function postOrder2(node) {
var stack = [];
var result = [];
stack.push(node);
while (stack.length > 0) {
var tmp = stack[stack.length-1];
if (tmp.left && tmp.left != node && tmp.right != node) {
stack.push(tmp.left);
} else if (tmp.right && tmp.right != node) {
stack.push(tmp.right);
} else {
var cnode = stack.pop();
result.push(cnode.value);
node = tmp;
}
}
return result;
}
var tree = arrToTree([1,2,3,4,5,'',6,7,8,9,'','','','','','','',10]);
console.log(tree);
console.log(postOrder2(tree));