JavaScript 打印二叉树左视图的实现返回不正确的结果

Question

我正在尝试打印在 geeksforgeeks 上 here 看到的二叉树的左视图。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

链接页面代码的区别是

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

对

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

您在这里增加了 level 两次，而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递增：

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

Answer 2

使用哈希table在几行代码中找到树的左右视图。

right_view(root,num, result) {
    if(root == null) {
        return 0
    }
    right_view(root.Left, num+1, result)
    right_view(root.Right, num+1, result)
    result[num] = root.Value
}

left_view(root,num, result) {
    if(root == null) {
        return 0
    }
    left_view(root.Left, num+1, result)
    left_view(root.Right, num+1, result)
    if(result[num] == undefined) {
        result[num] = root.Value
    }
}

用根节点调用函数。

right_view_result = {}
right_view(root,1,right_view_result)
console.log(right_view_result)

用根节点调用函数。

left_view_result = {}
left_view(root,1,left_view_result)
console.log(left_view_result)

JavaScript 打印二叉树左视图的实现返回不正确的结果

JavaScript implementation of printing left view of binary tree is returning incorrect result

javascript

recursion

binary-tree

node.js

JS代码

用根节点调用函数。

用根节点调用函数。