Bitap algorithm

function bitapSearch(text: string, pattern: string): string | null {
    const m = pattern.length;

    if (m === 0) {
        return text;
    }

    // Initialize the bit array R.
    const R: boolean[] = new Array(m + 1).fill(false);
    R[0] = true;

    for (let i = 0; i < text.length; i++) {
        // Update the bit array.
        for (let k = m; k >= 1; k--) {
            R[k] = R[k - 1] && (text[i] === pattern[k - 1]);
        }

        if (R[m]) {
            return text.substring(i - m + 1, i + 1);
        }
    }

    return null;
}

// Example usage:
const text = "this is a simple example";
const pattern = "simple";
const result = bitapSearch(text, pattern);
console.log(result); // Output: "simple"