Added isunique from ctci

Author: rampatra

src/main/java/com/rampatra/misc/RightShiftOperator.java renamed to src/main/java/com/rampatra/bits/RightShiftOperator.java

@@ -1,16 +1,13 @@
-package com.rampatra.misc;
+package com.rampatra.bits;
 
 /**
- * Created by IntelliJ IDEA.
+ * {@code >>} shifts bits to right filling left bits with the left most
+ * bit (most significant bit). Also called signed right shift.
+ * {@code >>>} shifts bits to the right filling left bits
+ * with 0. Also called unsigned right shift.
  *
- * @author: ramswaroop
- * @date: 6/2/15
- * @time: 3:26 PM
- */
-
-/**
- * {@code >>} shifts bits to right filling left bits with the left most bit (most significant bit)
- * {@code >>>} shifts bits to the right filling left bits with 0
+ * @author rampatra
+ * @since 6/2/15
  */
 public class RightShiftOperator {
 

src/main/java/com/rampatra/bits/ShiftByNegativeNumber.java

@@ -0,0 +1,25 @@
+package com.rampatra.bits;
+
+/**
+ * Understanding shifting in Java. What happens when you shift a number by a negative number.
+ *
+ * @author rampatra
+ * @link https://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.19
+ * @link https://stackoverflow.com/a/10516830/1385441
+ * @since 18/11/2018
+ */
+public class ShiftByNegativeNumber {
+    /**
+     * These both are the same as in java if the left operand is int only the low five bits are considered
+     * for shifting and if the left operand is a long then the low six bits are considered.
+     * Binary representation of -2 is 11.....11110. The last 5 bits are 11110 which is 30.
+     *
+     * @param args
+     */
+    public static void main(String[] args) {
+        int v1 = 1 << -2;
+        int v2 = 1 << 30;
+        System.out.println(v1);
+        System.out.println(v2);
+    }
+}

src/main/java/com/rampatra/ctci/IsUnique.java

@@ -0,0 +1,51 @@
+package com.rampatra.ctci;
+
+/**
+ * @author rampatra
+ * @since 18/11/2018
+ */
+public class IsUnique {
+
+    private static boolean hasAllUniqueCharacters(String str) {
+        if (str == null || str.length() > 128) return false;
+
+        boolean[] charSet = new boolean[128]; // assuming the string contains only ASCII characters
+        for (int i = 0; i < str.length(); i++) {
+            int charVal = str.charAt(i);
+            if (charSet[charVal]) {
+                return false;
+            }
+            charSet[charVal] = true;
+        }
+        return true;
+    }
+
+    private static boolean hasAllUniqueCharactersWhenStringContainsAllLowercase(String s) {
+        int checker = 0;
+        for (int i = 0; i < s.length(); i++) {
+            int charValue = s.charAt(i) - 'a';
+            if ((checker & (1 << charValue)) > 0) {
+                return false;
+            }
+            checker |= (1 << charValue);
+        }
+        return true;
+    }
+
+    public static void main(String[] args) {
+        String s = "ram";
+        System.out.println(hasAllUniqueCharacters(s));
+        s = "rama";
+        System.out.println(hasAllUniqueCharacters(s));
+        s = "ramA";
+        System.out.println(hasAllUniqueCharacters(s));
+        System.out.println("-------");
+        s = "ram";
+        System.out.println(hasAllUniqueCharactersWhenStringContainsAllLowercase(s));
+        s = "rama";
+        System.out.println(hasAllUniqueCharactersWhenStringContainsAllLowercase(s));
+        // not working as the input contains different cases
+        s = "ramA";
+        System.out.println(hasAllUniqueCharactersWhenStringContainsAllLowercase(s));
+    }
+}