Provide a straightforward solution that does not use string functions.

A common interview challenge is to manipulate or analyze strings without relying on built‑in string methods. One approach is to treat the string as an array of characters and perform operations directly on that array. For example, to reverse a string, you can swap characters from the ends toward the center using a simple loop:

function reverse(str) {
  let arr = str.split(''); // or treat as array if language allows
  let i = 0, j = arr.length - 1;
  while (i < j) {
    let temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
    i++; j--;
  }
  return arr.join('');
}

If you truly cannot use any string methods, you can work with the underlying character codes. In C, you can use a char array and swap s[i] and s[j]. In JavaScript, you can use Array.from(str) to get an array of code points and then manipulate it. The key idea is to avoid high‑level string utilities and rely on basic loops, indexing, and, if needed, bitwise or arithmetic operations. This keeps the solution straightforward, efficient (O(n) time, O(1) extra space for in‑place reversal), and demonstrates a solid grasp of low‑level string handling.