k consecutive characters done

Author: rampatra

src/main/java/com/rampatra/strings/KeepOnlyKConsecutiveLetters.java

@@ -0,0 +1,53 @@
+package com.rampatra.strings;
+
+/**
+ * @author rampatra
+ * @since 30/11/2018
+ */
+public class KeepOnlyKConsecutiveLetters {
+
+    /**
+     * A method which takes a string {@code str} and a number {@code k} and
+     * returns a string with at most {@code k} consecutive characters in the
+     * string.
+     * <p>
+     * For example,
+     * 1) aaaaaabbbbbccccc, 3 -> aaabbbccc
+     * 2) abc, 2 -> abc
+     * 3) aabbccc, 3 -> aabbccc
+     *
+     * @param str input string
+     * @param k
+     * @return
+     */
+    private static String keepOnlyKConsecutiveLetters(String str, int k) {
+        StringBuilder sb = new StringBuilder();
+
+        for (int i = 0; i < str.length(); i++) {
+            char ch = str.charAt(i);
+
+            for (int j = 0; i + j < str.length() && j < k; j++) {
+                char ch2 = str.charAt(i + j);
+                if (ch2 == ch) {
+                    sb.append(ch2);
+                } else {
+                    break;
+                }
+            }
+
+            while (i + 1 < str.length() && str.charAt(i + 1) == str.charAt(i)) {
+                i++;
+            }
+        }
+        return sb.toString();
+    }
+
+    public static void main(String[] args) {
+        System.out.println("aaaaabbbbbccccc, 5: " + keepOnlyKConsecutiveLetters("aaaaabbbbbccccc", 5));
+        System.out.println("aaaaabbbbbccccc, 2: " + keepOnlyKConsecutiveLetters("aaaaabbbbbccccc", 2));
+        System.out.println("aaaaabbbbbccccc, 1: " + keepOnlyKConsecutiveLetters("aaaaabbbbbccccc", 1));
+        System.out.println("aabbcc, 2: " + keepOnlyKConsecutiveLetters("aabbcc", 2));
+        System.out.println("aabbcc, 0: " + keepOnlyKConsecutiveLetters("aabbcc", 0));
+        System.out.println("abc, 2: " + keepOnlyKConsecutiveLetters("abc", 2));
+    }
+}