All Nodes Distance K In Binary Tree Problem


Description

LeetCode Problem 863.

Given the root of a binary tree, the value of a target node target, and an integer k, return an array of the values of all nodes that have a distance k from the target node.

You can return the answer in any order.

Example 1:

1
2
3
Input: root = [3,5,1,6,2,0,8,null,null,7,4], target = 5, k = 2
Output: [7,4,1]
Explanation: The nodes that are a distance 2 from the target node (with value 5) have values 7, 4, and 1.

Example 2:

1
2
Input: root = [1], target = 1, k = 3
Output: []

Constraints:

  • The number of nodes in the tree is in the range [1, 500].
  • 0 <= Node.val <= 500
  • All the values Node.val are unique.
  • target is the value of one of the nodes in the tree.
  • 0 <= k <= 1000


Sample C++ Code

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<TreeNode*> path(TreeNode *root, int val) {
        if (!root) 
            return {};
        if (root->val == val) 
            return {root};
        vector<TreeNode*> l, r;
        l = path(root->left, val);
        r = path(root->right, val);
        if (l.size()) {
            l.push_back(root); 
            return l;
        }
        if (r.size()) {
            r.push_back(root); 
            return r;
        }
        return {};
    }
    
    void distance(TreeNode *root, int k, TreeNode* before, vector<int> &ans) {
        if (!root || root == before) 
            return;
        distance(root->left, k - 1, before, ans);
        distance(root->right, k - 1, before, ans);
        if (k == 0) 
            ans.push_back(root->val);
        return;
    }
    
    vector<int> distanceK(TreeNode* root, TreeNode* target, int k) {
        vector<TreeNode*> v = path(root, target->val);
        vector<int> ans;
        for (int i = 0; i < v.size() && k >= i; i++)
            distance(v[i], k - i, i == 0 ? NULL : v[i - 1], ans);
        return ans;
    }
};




Related Posts

Vertical Order Traversal Of A Binary Tree Problem

LeetCode 987. Given the root of a binary tree, calculate...

Univalued Binary Tree Problem

LeetCode 965. A binary tree is uni-valued if every node...

Sum Of Distances In Tree Problem

LeetCode 834. There is an undirected connected tree with n...

Smallest Subtree With All The Deepest Nodes Problem

LeetCode 865. Given the root of a binary tree, the...

Smallest String Starting From Leaf Problem

LeetCode 988. You are given the root of a binary...

Similar String Groups Problem

LeetCode 839. Two strings Xand Yare similar if we can...