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Problem 145

Medium

1 · Worked examples

0 / 3

Type an input and write what you think is the output . Each problem is converted to Web Assembly, so any possible input will show the corresponding output. Only correct predictions count.

solution()
returns

2 · Which problem is it?

Locked until you have predicted 3 outputs correctly.

The accepted solution

1struct Node {
2 int val;
3 Node* left;
4 Node* right;
5};
6
7Node* build(const vector<optional<int>>& level) {
8
9 if (level.empty() || !level[0]) {
10 return nullptr;
11 }
12
13 Node* root = new Node{*level[0], nullptr, nullptr};
14
15 queue<Node*> q;
16 q.push(root);
17
18 int i = 1;
19 int n = level.size();
20
21 while (!q.empty() && i < n) {
22
23 Node* node = q.front();
24 q.pop();
25
26 if (level[i]) {
27 node->left = new Node{*level[i], nullptr, nullptr};
28 q.push(node->left);
29 }
30
31 i++;
32
33 if (i < n && level[i]) {
34 node->right = new Node{*level[i], nullptr, nullptr};
35 q.push(node->right);
36 }
37
38 i++;
39 }
40
41 return root;
42}
43
44Node* meet(Node* node, int p, int q) {
45
46 while (node) {
47
48 if (p < node->val && q < node->val) {
49 node = node->left;
50
51 } else if (p > node->val && q > node->val) {
52 node = node->right;
53
54 } else {
55 return node;
56 }
57 }
58
59 return nullptr;
60}
61
62int solution(const vector<optional<int>>& level, int p, int q) {
63
64 Node* root = build(level);
65 Node* found = meet(root, p, q);
66
67 if (!found) {
68 return -1;
69 }
70
71 return found->val;
72}

Names have been stripped. The signature is the only clue you get for free. Compiled as C++20 with the standard headers and using namespace std; already in scope.