Compress string

Author: rampatra

src/main/java/com/ctci/arraysandstrings/StringCompression.java

@@ -0,0 +1,38 @@
+package com.ctci.arraysandstrings;
+
+/**
+ * @author rampatra
+ * @since 24/11/2018
+ */
+public class StringCompression {
+
+    /**
+     * Compresses the string {@code s} such that a string {@code aabccccaaa} becomes {@code a2b1c4a3}.
+     * Also, if the compressed string is not shorter than the original, returns the original string.
+     *
+     * @param str input string containing only a-z characters, both cases
+     * @return which ever is the shorter string
+     */
+    private static String compressString(String str) {
+        StringBuilder compressedSb = new StringBuilder();
+        int countConsecutive = 0;
+        for (int i = 0; i < str.length(); i++) {
+            countConsecutive++;
+
+            /* If next character is different than current, append this char to result. */
+            if (i + 1 >= str.length() || str.charAt(i) != str.charAt(i + 1)) {
+                compressedSb.append(str.charAt(i));
+                compressedSb.append(countConsecutive);
+                countConsecutive = 0;
+            }
+        }
+        return compressedSb.length() < str.length() ? compressedSb.toString() : str;
+    }
+
+    public static void main(String[] args) {
+        System.out.println("aabccccaaa: " + compressString("aabccccaaa"));
+        System.out.println("abcd: " + compressString("abcd"));
+        System.out.println("a: " + compressString("a"));
+        System.out.println("aabcccccccccccccccccccccccccaaa: " + compressString("aabcccccccccccccccccccccccccaaa"));
+    }
+}