#include <iostream>
#include <vector>
#include <cctype>
/**
* @brief Reverses only the alphabetic characters in a character vector in-place,
* leaving special characters, spaces, and digits in their original positions.
*
* @param vec Reference to the character vector to modify.
*/
void reverseOnlyLetters(std::vector<char>& vec) {
if (vec.empty()) {
return; // Guard against empty vectors
}
int left = 0;
int right = static_cast<int>(vec.size()) - 1;
// Use a two-pointer approach moving inward from both ends
while (left < right) {
// Advance left pointer until it points to an alphabetic character
while (left < right && !std::isalpha(static_cast<unsigned char>(vec[left]))) {
left++;
}
// Move right pointer backward until it points to an alphabetic character
while (left < right && !std::isalpha(static_cast<unsigned char>(vec[right]))) {
right--;
}
// Swap the valid letters found at both pointers using std::swap
if (left < right) {
std::swap(vec[left], vec[right]);
left++;
right--;
}
}
}
int main() {
// Input string converted to a standard vector of characters
std::string input = "a#b$%c&*(def!";
std::vector<char> vec(input.begin(), input.end());
std::cout << "Original: ";
for (char ch : vec) {
std::cout << ch;
}
std::cout << '\n';
// Apply the reversal function in-place
reverseOnlyLetters(vec);
std::cout << "Reversed: ";
for (char ch: vec) {
std::cout << ch;
}
}
/*
run:
Original: a#b$%c&*(def!
Reversed: f#e$%d&*(cba!
*/
