706. Design HashMap

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

To be specific, your design should include these functions:

  • put(key, value) : Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value.
  • get(key): Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
  • remove(key) : Remove the mapping for the value key if this map contains the mapping for the key.


Example:

MyHashMap hashMap = new MyHashMap();
hashMap.put(1, 1);          
hashMap.put(2, 2);         
hashMap.get(1);            // returns 1
hashMap.get(3);            // returns -1 (not found)
hashMap.put(2, 1);          // update the existing value
hashMap.get(2);            // returns 1 
hashMap.remove(2);          // remove the mapping for 2
hashMap.get(2);            // returns -1 (not found) 


Note:

  • All keys and values will be in the range of [0, 1000000].
  • The number of operations will be in the range of [1, 10000].
  • Please do not use the built-in HashMap library.

Rust Solution

#[derive(Default)]
struct MyHashMap {
    v: Vec<i32>,
}

const LIMIT: usize = 1_000_000;

impl MyHashMap {
    fn new() -> Self {
        MyHashMap {
            v: vec![-1; LIMIT + 1],
        }
    }

    fn put(&mut self, key: i32, value: i32) {
        self.v[key as usize] = value;
    }

    fn get(&self, key: i32) -> i32 {
        self.v[key as usize]
    }

    fn remove(&mut self, key: i32) {
        self.v[key as usize] = -1;
    }
}

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