#include <iostream>
#include <string>
#include <cctype>
/* ---------------------------------------------------------
Compress: turn "aaabbcccc" into "a3b2c4"
This is run-length encoding (RLE)
--------------------------------------------------------- */
std::string compress(const std::string &s) {
if (s.empty()) return ""; // Edge case: empty string
std::string out; // Result string
int count = 1; // Count of repeated characters
// Start from index 1 and compare with previous character
for (size_t i = 1; i <= s.size(); i++) {
// If still repeating the same character, increase count
if (i < s.size() && s[i] == s[i - 1]) {
count++;
}
else {
// Character changed OR reached end of string
out += s[i - 1]; // Add the character
out += std::to_string(count); // Add how many times it repeated
count = 1; // Reset counter
}
}
return out;
}
/* ---------------------------------------------------------
Decompress: turn "a3b2c4" into "aaabbcccc"
Reads a letter, then reads digits, expands them.
--------------------------------------------------------- */
std::string decompress(const std::string &s) {
std::string out; // Result string
char currentChar = '\0'; // The character being processed
std::string number; // Digits representing the count
for (char c : s) {
if (std::isalpha(static_cast<unsigned char>(c))) { // Found a letter
// If we already have a previous letter + number, expand it
if (currentChar != '\0' && !number.empty()) {
out.append(std::stoi(number), currentChar);
}
currentChar = c; // Start new character
number.clear(); // Reset number buffer
}
else if (std::isdigit(static_cast<unsigned char>(c))) { // Found a digit
number += c; // Build multi-digit number
}
}
// Handle the last character + number pair
if (currentChar != '\0' && !number.empty()) {
out.append(std::stoi(number), currentChar);
}
return out;
}
int main() {
std::string s = "wwwwwwwwwwwwbwwwwwwwwwwbbbwwwwwwccccwwwwwwwwwwww";
std::string c = compress(s);
std::string d = decompress(c);
std::cout << "Original: " << s << std::endl;
std::cout << "Compressed: " << c << std::endl;
std::cout << "Decompressed: " << d << std::endl;
}
/*
run:
Original: wwwwwwwwwwwwbwwwwwwwwwwbbbwwwwwwccccwwwwwwwwwwww
Compressed: w12b1w10b3w6c4w12
Decompressed: wwwwwwwwwwwwbwwwwwwwwwwbbbwwwwwwccccwwwwwwwwwwww
*/
