What is the Time Complexity for Generating a Hash Value from a String in a Hashtable?

What is the time complexity associated with computing the hash value of a string when using a hashtable?

// Example of a simple string hashing function
function hashString(str) {
    let hash = 0;
    for (let i = 0; i < str.length; i++) {
        hash += str.charCodeAt(i);
    }
    return hash;
}

The time complexity of generating a hash value for a string in a hashtable primarily depends on the length of the string being hashed. When using efficient hash functions, this complexity is generally linear with respect to the string length, O(n).

// Example of a more efficient hashing algorithm
function optimizedHashString(str) {
    let hash = 5381;
    for (let i = 0; i < str.length; i++) {
        hash = (hash * 33) ^ str.charCodeAt(i);
    }
    return hash >>> 0; // Ensure a non-negative number
}

Causes

• The hash function iterates over each character in the string to compute its hash value.
• The complexity increases with the string length, requiring more time to process longer strings.

Solutions

• Optimize your hash function to minimize unnecessary computations.
• Consider using built-in hashing libraries that are optimized for performance.

Mistake: Using a hash function without considering string length.

Solution: Always evaluate the efficiency of your hash function based on the expected string lengths.

Mistake: Not handling collisions in the hashtable properly.

Solution: Implement a good collision resolution strategy (chaining or open addressing).