打印二叉树左 View 的 JavaScript 实现返回错误结果

Question

我正在尝试打印二叉树的左 View ，如here所示关于geeksforgeeks。由于某种原因它不起作用，我怀疑它与 max_level 有关。结果是 [ 12, 10, 30, 25, 40 ]，我期待 [12,10,25]。

JS代码

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

var leftViewUtil = function(root, level, max, result) {
    if (root === null) return;

    if (max.level < level) {
        max.level = level;
        result.arr.push(root.val);
    }

    leftViewUtil(root.left, ++level, max, result);
    leftViewUtil(root.right, ++level, max, result);
};

var leftView = function(root) {
    var result = {
        arr: []
    };

    var max_level = {level: 0};

    leftViewUtil(root, 1, max_level, result);

    return result.arr;
};

root = new Node(12);
root.left = new Node(10);
root.right = new Node(30);
root.right.left = new Node(25);
root.right.right = new Node(40);

var run = function() {
    console.log(leftView(root));
};

run();

Answer 1

链接页面上的代码之间的差异是

// Recur for left and right subtrees
leftViewUtil(root->left, level+1, max_level);
leftViewUtil(root->right, level+1, max_level);

对比

leftViewUtil(root.left, ++level, max, result);
leftViewUtil(root.right, ++level, max, result);

您在这里将 level 增加两次，同时您应该将相同的值传递给两个递归调用。适当使用 level+1 ，或者在调用之前进行增量:

++level;
leftViewUtil(root.left, level, max, result);
leftViewUtil(root.right, level, max, result);