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.
Locked until you have predicted 4 outputs correctly.
| 1 | struct Cell { |
| 2 | int key = 0; |
| 3 | int value = 0; |
| 4 | Cell* prev = nullptr; |
| 5 | Cell* next = nullptr; |
| 6 | }; |
| 7 | |
| 8 | struct Cache { |
| 9 | int cap; |
| 10 | Cell head, tail; |
| 11 | unordered_map<int, Cell*> at; |
| 12 | |
| 13 | explicit Cache(int capacity) : cap(capacity) { |
| 14 | head.next = &tail; |
| 15 | tail.prev = &head; |
| 16 | } |
| 17 | |
| 18 | void unlink(Cell* c) { |
| 19 | c->prev->next = c->next; |
| 20 | c->next->prev = c->prev; |
| 21 | } |
| 22 | |
| 23 | void toFront(Cell* c) { |
| 24 | c->next = head.next; |
| 25 | c->prev = &head; |
| 26 | head.next->prev = c; |
| 27 | head.next = c; |
| 28 | } |
| 29 | |
| 30 | int get(int key) { |
| 31 | |
| 32 | auto it = at.find(key); |
| 33 | |
| 34 | if (it == at.end()) { |
| 35 | return -1; |
| 36 | } |
| 37 | |
| 38 | Cell* cell = it->second; |
| 39 | |
| 40 | unlink(cell); |
| 41 | toFront(cell); |
| 42 | |
| 43 | return cell->value; |
| 44 | } |
| 45 | |
| 46 | void put(int key, int value) { |
| 47 | |
| 48 | auto it = at.find(key); |
| 49 | |
| 50 | if (it != at.end()) { |
| 51 | |
| 52 | Cell* cell = it->second; |
| 53 | cell->value = value; |
| 54 | |
| 55 | unlink(cell); |
| 56 | toFront(cell); |
| 57 | return; |
| 58 | } |
| 59 | |
| 60 | if ((int)at.size() == cap) { |
| 61 | |
| 62 | Cell* stale = tail.prev; |
| 63 | |
| 64 | unlink(stale); |
| 65 | at.erase(stale->key); |
| 66 | delete stale; |
| 67 | } |
| 68 | |
| 69 | Cell* fresh = new Cell{key, value, nullptr, nullptr}; |
| 70 | |
| 71 | at[key] = fresh; |
| 72 | toFront(fresh); |
| 73 | } |
| 74 | }; |
| 75 | |
| 76 | vector<string> solution(int capacity, const vector<string>& ops, |
| 77 | const vector<int>& keys, |
| 78 | const vector<int>& values) { |
| 79 | |
| 80 | Cache cache(capacity); |
| 81 | vector<string> ans; |
| 82 | |
| 83 | int n = ops.size(); |
| 84 | |
| 85 | for (int i = 0; i < n; i++) { |
| 86 | |
| 87 | if (ops[i] == "put") { |
| 88 | cache.put(keys[i], values[i]); |
| 89 | ans.push_back("null"); |
| 90 | } else { |
| 91 | int got = cache.get(keys[i]); |
| 92 | ans.push_back(to_string(got)); |
| 93 | } |
| 94 | } |
| 95 | |
| 96 | return ans; |
| 97 | } |
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.