Update in Hash Table

Update in Hash Table

The update operation involves modifying the value associated with an existing key in a hash table. If the key is not present, it may require an insertion.

Steps for Update

1. Hash the Key: Use a hash function to find the index.
2. Update the Value: Modify the value associated with the key if it exists.
3. Handle Key Absence: If the key does not exist, you can choose to insert it instead.

Time Complexity

• Average Case: $O(1)$
• Worst Case: $O(n)$

Example Code (Python)

class HashTable:
    def __init__(self):
        self.table = {}

    def update(self, key, value):
        self.table[key] = value

# Example usage
hash_table = HashTable()
hash_table.table = {'apple': 10, 'banana': 20}
hash_table.update('apple', 30)  # Updates value

Example Code (Javascript)

class HashTable {
    constructor() {
        this.table = {};
    }

    update(key, value) {
        this.table[key] = value;
    }
}

// Example usage
const hashTable = new HashTable();
hashTable.table = { 'apple': 10, 'banana': 20 };
hashTable.update('apple', 30);  // Updates the value for 'apple'
console.log(hashTable.table);    // Output: { 'apple': 30, 'banana': 20 }

Conclusion

Update is critical for modifying data in hash tables, making them adaptable and suitable for dynamic applications.