String compression using run length encoding

“String Compression Algorithm” or “Run Length Encoding” happens when you compress a string, and the consecutive duplicates of each string are replaced with the character, followed by the consecutive, repeated character count.

For example:

After string compression, the string “aaaabbcddddd” would return “a4b2c1d5”.

You may not have seen such strings in texts, but image and video files almost always have long repeating sequences. Some uses of run-length encoding include:

Compressing faxed documents
Compressing JPEG images

In images, colors are replaced by the character, or color, followed by the number of times that color repeats itself. This is shown below:

#include<iostream>
#include <string>
using namespace std;
 
void compress(string s)
{
    int num = s.length(); //calculating length of the string
    int i=0; 
    while ( i < num) {
 
        // Counting the repetitions of each character 
        int repetition = 1;
        while (s[i] == s[i+1] && i < num-1 ) {
            repetition++;
            i++;
        }
        
        // Print character and its count
        cout << s[i] << repetition;
        i++;
    }
}
 
int main()
{
    string str = "aaaabbcddddd";
    compress(str);
}

#include <iostream>
#include <string>
using namespace std;
void compress(string s)
{
    int num = s.length(); // calculating length of the string
    int i = 0;
    while (i < num) 
    {
        // Counting the repetitions of each character 
        int repetition = 1;
        while (s[i] == s[i+1] && i < num - 1) 
        {
            repetition++;
            i++;
        }
        
        // Print character and its count using the escape character approach
        cout << s[i];
        if (repetition > 1) 
        {
            cout << s[i] << repetition;
        }
        i++;
    }
}
int main()
{
    string str = "aaaabbcddddd";
    compress(str);
    return 0;
}

Line 12: The repetition variable is initialized to 1 to count the occurrences of each character.
Lines 13–17: While the current character is the same as the next character and the end of the string hasn't been reached, the repetition count is incremented, and the index i is incremented to move to the next character.
Lines 21–25: After counting consecutive occurrences, the current character is printed. If the repetition count is greater than 1, the character is printed again followed by its count, representing the escape character approach for run-length encoding. Finally, the index i is incremented to move to the next character in the string.

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)

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String compression using run length encoding

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