reverseString

reverseString refers to reversing the order of characters in a string to produce a new string that contains the input characters in reverse sequence. It is a common operation in text processing, used in palindrome checks, data transformation, and various string manipulation tasks.

Implementation typically falls into two categories. The simplest approach builds a new string by iterating from the end of the input to the beginning and appending each character. A more memory-efficient variant reverses characters in place when the language provides a mutable character array, by swapping symmetric positions from the ends toward the center. In terms of complexity, both approaches process each character exactly once, giving a time complexity of O(n). The non-mutating version uses O(n) extra space for the result, while an in-place version achieves O(1) extra space.

Unicode and encoding considerations are important. Reversing can affect grapheme clusters, surrogate pairs, or combining marks, depending on the language and encoding. Correct handling often requires reversing at the level of code points or grapheme clusters rather than raw code units.

Examples in common languages: in Python, s[::-1] returns the reversed string; in Java, new StringBuilder(s).reverse().toString() reverses the characters; in JavaScript, [...s].reverse().join('') or s.split('').reverse().join('') can be used, though some methods may mishandle certain Unicode sequences.

See also: palindrome, string manipulation, encoding.