161. Create a string by repeating the first character of another string.
162. Convert a string to hexadecimal.
163. Convert hexadecimal back to a string.
164. Swap the case of the first and last letter in a string.
165. Count the occurrences of each digit in a string.
166. Replace every alphabetic character in a string with its ASCII value.
167. Check if a string can be split into two identical halves.
168. Reverse the order of vowels in each word of a string.
169. Convert a string to its hexadecimal representation.
170. Find the second last word in a string.
171. Find the number of times the first character appears in a string.
172. Check if a string contains a palindrome as a substring.
173. Check if a string is a valid hexadecimal number.
174. Check if two strings are permutations of each other.
175. Swap every two adjacent characters in a string.
176. Find the length of the longest substring that contains no vowels.
177. Find the length of the shortest substring that contains all vowels.
178. Convert a string to Morse code.
179. Convert Morse code back to a string.
180. Replace each character in a string with its Unicode representation.
181. Create a string by concatenating the ASCII values of each character.
182. Reverse the case of all letters in a string.
183. Remove the first and last vowel in a string.
184. Create a string with all characters sorted by their ASCII values.
185. Replace the second character in every word with ''.
186. Remove all repeated characters from a string.
187. Find the second occurrence of a word in a string.
188. Replace all digits in a string with their word equivalents.
189. Replace every second vowel in a string with ''.
190. Convert a string to a valid JSON key.
191. Find the lexicographically largest substring in a string.
192. Find the lexicographically smallest substring in a string.
193. Check if two strings differ by exactly one character.
194. Check if two strings can be made identical by swapping two characters.
195. Count the number of different characters between two strings.
196. Convert a string into a valid HTML entity.
197. Reverse every third character in a string.
198. Check if a string is a valid hexadecimal color code.
199. Replace the first vowel in each word of a string with ''.
200. Find the number of consonants that appear more than once in a string.