二叉树的创建，插入，查找和比较

function TreeNode(){
    this.val = val;
    this.left = null;
    this.right = null;
}

function createBTree(aVal,fPredicate,pos){
    var node = {};
    pos = pos || 0;
    if(fPredicate(aVal,pos) || !aVal[pos]){
        return null;
    }
    else{
        node.val = aVal[pos];
        node.left = createBTree(aVal,fPredicate,2*pos+1);
        node.right = createBTree(aVal,fPredicate,2*pos+2);
    }
    return node;
}

function BTreeInsert(root,val,direction,node){
    if(root == null){
        return false;
    }
    if(root.val === val){
        switch(direction){
            case ‘left‘:
                if(root.left){
                    //throw new Error(‘left node already exists‘);
                    return false;
                }
                else{
                    root.left = node;
                }
                break;
            case ‘right‘:
                if(root.right){
                    //throw new Error(‘right node already exists‘);
                    return false;
                }
                else{
                    root.right = node;
                }
                break;
        }
    }
    else{
        BTreeInsert(root.left,node,val,direction);
        BTreeInsert(root.right,node,val,direction);
    }
    return true;
}

function DLRFind(root, val) {
    if (root == null) {
        return null;
    }
    if (root.val === val) {
        return root;
    }
    return DLRFind(root.left, val) || DLRFind(root.right, val);
}

function BTreeCompare(root1,root2){
    if(root1 == null && root2 == null){
        return true;
    }
    else if(root1 != null && root2 != null){
        return BTreeCompare(root1.left,root2.left)
            && BTreeCompare(root1.right,root2.right);
    }   
    else{
        return false;
    }
}

function BTreeClear(root){
    if(root == null){
        return true;
    }
    BTreeClear(root.left);
    BTreeClear(root.right);
    root = null;
    return true;
}

var root = createBTree([3, 2, 4, 6, 7, 8, 1, 0], function (aVal, pos) {
    return aVal[pos] == 0 || pos > 8
}, 0);
DLR(root);//output 3 2 6 7 4 8 1
DLRFind(root,2);//output node 2
DLRFind(root,11);//output null

function createBTree(aVal, fPredicate, pos) {
    var node = {};
    pos = pos || 0;
    if (fPredicate(aVal, pos) || !aVal[pos]) {
        return null;
    } else {
        node.val = aVal[pos];
        node.left = createBTree(aVal, fPredicate, 2 * pos + 1);
        node.right = createBTree(aVal, fPredicate, 2 * pos + 2);
    }
    return node;
}

function DLR(root) {
    if (root == null) {
        return null;
    } 
    else {
        console.log(‘d ‘ + root.val);
        DLR(root.left);
        DLR(root.right);
    }
}

function DLRFind(root, val) {
    if (root == null) {
        return null;
    }
    if (root.val === val) {
        return root;
    }
    return DLRFind(root.left, val) || DLRFind(root.right, val);
}