> ## Documentation Index
> Fetch the complete documentation index at: https://leetcode-py.wisl.dev/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> leetcode-py is a Python LeetCode practice environment generator with one CLI: lcpy. It is not a service or platform.
> Each problem is a directory under leetcode/ with README.md, solution.py, test_solution.py, helpers.py, and playground.ipynb. lcpy gen creates them from JSON templates bundled with the package.
> Examples are backed by tests; copy them verbatim.

# Design HashMap Python Solution with Tests

> Tested Python solution for LeetCode 706 with 13 pytest cases. Generate a practice environment with lcpy.

LeetCode 706, Easy. Topics: Array, Hash Table, Linked List, Design, Hash Function. [View on LeetCode](https://leetcode.com/problems/design-hash-map/description/).

Generate this problem as a practice environment: tested reference solution, 13 [parametrized pytest cases](/practice/testing), and a playground notebook:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 706   # by problem number
lcpy gen -s design_hash_map   # by problem name
```

## Problem

Design a HashMap without using any built-in hash table libraries.

Implement the `MyHashMap` class:

* `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`.

### Examples

```
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
myHashMap.get(3);    // return -1 (not found)
myHashMap.put(2, 1); // The map is now [[1,1], [2,1]] (update)
myHashMap.get(2);    // return 1
myHashMap.remove(2); // remove the mapping for 2, The map is now [[1,1]]
myHashMap.get(2);    // return -1 (not found)
```

### Constraints

* 0 \<= key, value \<= 10^6
* At most 10^4 calls will be made to `put`, `get`, and `remove`.

## Solution

Reference implementation from [solution.py on GitHub](https://github.com/wislertt/leetcode-py/blob/main/leetcode/design_hash_map/solution.py), full suite in [test\_solution.py](https://github.com/wislertt/leetcode-py/blob/main/leetcode/design_hash_map/test_solution.py):

```python theme={"theme":{"light":"github-light","dark":"github-dark"}}
class MyHashMap:
    # Time: O(n) init, O(1) ops
    # Space: O(n)
    def __init__(self) -> None:
        # Problem guarantees 0 <= key, value <= 10^6; -1 marks "no mapping".
        self._values: list[int] = [-1] * 1_000_001

    # Time: O(1)
    # Space: O(1)
    def put(self, key: int, value: int) -> None:
        self._values[key] = value

    # Time: O(1)
    # Space: O(1)
    def get(self, key: int) -> int:
        return self._values[key]

    # Time: O(1)
    # Space: O(1)
    def remove(self, key: int) -> None:
        self._values[key] = -1
```

## Complexity

| Time                | Space |
| ------------------- | ----- |
| O(n) init, O(1) ops | O(n)  |

## Tags

[NeetCode 250](/catalog/neetcode-250), [NeetCode All](/catalog/neetcode).