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Rle.java
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Rle.java
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package cryptography.encoding.rle;
import cryptography.Mode;
public class Rle {
/**
* Run-Length Encoding https://en.wikipedia.org/wiki/Run-length_encoding
*
* @param mode Encode or decode
* @param input string input
* @return string
*/
public static String rle(Mode mode, String input) {
StringBuilder str = new StringBuilder();
if (mode == Mode.ENCODE) {
int il = input.length();
for (int i = 0; i < il; i++) {
int count = 1;
while (i < il - 1 && input.charAt(i) == input.charAt(i + 1)) {
count++;
i++;
}
str.append(input.charAt(i)).append(count);
}
return str.toString();
}
if (mode == Mode.DECODE) {
char[] stArr = input.toCharArray();
char lastChar = 0;
for (int p = 0; p < stArr.length; p++) {
char s = stArr[p];
if (!Character.isDigit(s)) {
lastChar = s;
str.append(s);
} else {
int e = digitCount(stArr, p);
int n = Integer.parseInt(String.valueOf(input.substring(p, (p + e))));
for (int i = 0; i < n - 1; i++) {
str.append(lastChar);
}
}
}
}
return str.toString();
}
public static int digitCount(char[] stArr, int currentPos) {
int count = 0;
for (int p = currentPos; p < stArr.length; p++) {
if (Character.isDigit(stArr[p])) {
count++;
} else {
break;
}
}
return count;
}
}