diff --git a/String/BoothsAlgorithm.js b/String/BoothsAlgorithm.js new file mode 100644 index 0000000000..c92558e8b4 --- /dev/null +++ b/String/BoothsAlgorithm.js @@ -0,0 +1,79 @@ +/** + * Booth's Algorithm finds the lexicographically minimal rotation of a string. + * Time Complexity: O(n) - Linear time where n is the length of input string + * Space Complexity: O(n) - Linear space for failure function array + * For More Visit - https://en.wikipedia.org/wiki/Booth%27s_multiplication_algorithm + * @example + * Input: "baca" + * All possible rotations: + * - "baca" + * - "acab" + * - "caba" + * - "abac" + * Output: "abac" (lexicographically smallest) + * + * How it works: + * 1. Doubles the input string to handle all rotations + * 2. Uses failure function (similar to KMP) to find minimal rotation + * 3. Maintains a pointer to the start of minimal rotation found so far + * @param {string} str - Input string to find minimal rotation + * @returns {string} - Lexicographically minimal rotation of the input string + * @throws {Error} - If input is not a string or is empty + */ +export function findMinimalRotation(str) { + if (typeof str !== 'string') { + throw new Error('Input must be a string') + } + + if (str.length === 0) { + throw new Error('Input string cannot be empty') + } + + // Double the string for rotation comparison + // This allows us to check all rotations by just sliding a window + const s = str + str + const n = s.length + + // Initialize failure function array + const f = new Array(n).fill(-1) + let k = 0 // Starting position of minimal rotation + + //Algorithm's implementation + // Iterate through the doubled string + // j is the current position we're examining + for (let j = 1; j < n; j++) { + // i is the length of the matched prefix in the current candidate + // Get the failure function value for the previous position + let i = f[j - k - 1] + // This loop handles the case when we need to update our current minimal rotation + // It compares characters and finds if there's a better (lexicographically smaller) rotation + while (i !== -1 && s[j] !== s[k + i + 1]) { + // If we find a smaller character, we've found a better rotation + // Update k to the new starting position + if (s[j] < s[k + i + 1]) { + // j-i-1 gives us the starting position of the new minimal rotation + k = j - i - 1 + } + // Update i using the failure function to try shorter prefixes + i = f[i] + } + + // This block updates the failure function and handles new character comparisons + if (i === -1 && s[j] !== s[k + i + 1]) { + // If current character is smaller, update the minimal rotation start + if (s[j] < s[k + i + 1]) { + k = j + } + //If no match found,mark failure function accordingly + f[j - k] = -1 + } else { + //If match found, extend the matched length + f[j - k] = i + 1 + } + } + // After finding k (the starting position of minimal rotation): + // 1. slice(k): Take substring from position k to end + // 2. slice(0, k): Take substring from start to position k + // 3. Concatenate them to get the minimal rotation + return str.slice(k) + str.slice(0, k) +} diff --git a/String/test/BoothsAlgorithm.test.js b/String/test/BoothsAlgorithm.test.js new file mode 100644 index 0000000000..f219820199 --- /dev/null +++ b/String/test/BoothsAlgorithm.test.js @@ -0,0 +1,53 @@ +import { findMinimalRotation } from '../BoothsAlgorithm' + +describe('BoothsAlgorithm', () => { + it('should throw an error if input is not a string', () => { + expect(() => findMinimalRotation(null)).toThrow('Input must be a string') + expect(() => findMinimalRotation(undefined)).toThrow( + 'Input must be a string' + ) + expect(() => findMinimalRotation(123)).toThrow('Input must be a string') + expect(() => findMinimalRotation([])).toThrow('Input must be a string') + }) + + it('should throw an error if input string is empty', () => { + expect(() => findMinimalRotation('')).toThrow( + 'Input string cannot be empty' + ) + }) + + it('should find minimal rotation for simple strings', () => { + expect(findMinimalRotation('abc')).toBe('abc') + expect(findMinimalRotation('bca')).toBe('abc') + expect(findMinimalRotation('cab')).toBe('abc') + }) + + it('should handle strings with repeated characters', () => { + expect(findMinimalRotation('aaaa')).toBe('aaaa') + expect(findMinimalRotation('aaab')).toBe('aaab') + expect(findMinimalRotation('baaa')).toBe('aaab') + }) + + it('should handle strings with special characters', () => { + expect(findMinimalRotation('12#$')).toBe('#$12') + expect(findMinimalRotation('@abc')).toBe('@abc') + expect(findMinimalRotation('xyz!')).toBe('!xyz') + }) + + it('should handle longer strings', () => { + expect(findMinimalRotation('algorithm')).toBe('algorithm') + expect(findMinimalRotation('rithmalgo')).toBe('algorithm') + expect(findMinimalRotation('gorithmal')).toBe('algorithm') + }) + + it('should be case sensitive', () => { + expect(findMinimalRotation('AbC')).toBe('AbC') + expect(findMinimalRotation('BcA')).toBe('ABc') + expect(findMinimalRotation('CAb')).toBe('AbC') + }) + + it('should handle palindromes', () => { + expect(findMinimalRotation('radar')).toBe('adarr') + expect(findMinimalRotation('level')).toBe('ellev') + }) +})
Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.
Alternative Proxies: