Leetcode 706. Design HashMap

  • MyHashMap() initializes the object with an empty map.
  • void put(int key, int value) inserts a (key, value) pair into the HashMap. If the key already exists in the map, update the corresponding value.
  • int get(int key) returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
  • void remove(key) removes the key and its corresponding value if the map contains the mapping for the key.
Input
["MyHashMap", "put", "put", "get", "get", "put", "get", "remove", "get"]
[[], [1, 1], [2, 2], [1], [3], [2, 1], [2], [2], [2]]
Output
[null, null, null, 1, -1, null, 1, null, -1]
Explanation
MyHashMap myHashMap = new MyHashMap();
myHashMap.put(1, 1); // The map is now [[1,1]]
myHashMap.put(2, 2); // The map is now [[1,1], [2,2]]
myHashMap.get(1); // return 1, The map is now [[1,1], [2,2]]
myHashMap.get(3); // return -1 (i.e., not found), The map is now [[1,1], [2,2]]
myHashMap.put(2, 1); // The map is now [[1,1], [2,1]] (i.e., update the existing value)
myHashMap.get(2); // return 1, The map is now [[1,1], [2,1]]
myHashMap.remove(2); // remove the mapping for 2, The map is now [[1,1]]
myHashMap.get(2); // return -1 (i.e., not found), The map is now [[1,1]]
  • 0 <= key, value <= 106
  • At most 104 calls will be made to put, get, and remove.
class MyHashMap {
public:
vector<list<pair<int,int>>> data;
size_t size = 10000;

MyHashMap() {
data.resize(size);
}

void put(int key, int value) {
for (auto& e: data[key%size]) {
if (e.first == key) {
e.second = value;
return;
}
}
data[key % size].push_back(make_pair(key, value));
}

int get(int key) {
for (auto& e: data[key%size]) {
if (e.first == key) {
return e.second;
}
}
return -1;
}

void remove(int key) {
list<pair<int, int>>::iterator itr = data[key%size].begin();
for (; itr != data[key%size].end(); itr++) {
if (itr->first == key) {
itr = data[key%size].erase(itr);
return;
}
}
}
};

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