Merge branch 'master' of https://github.com/Rupa-Rd/Java

Author: Rupa-Rd

DIRECTORY.md

@@ -42,6 +42,7 @@
             * [AES](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/AES.java)
             * [AESEncryption](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/AESEncryption.java)
             * [AffineCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/AffineCipher.java)
+            * [Autokey](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/Autokey.java)
             * [Blowfish](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/Blowfish.java)
             * [Caesar](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/Caesar.java)
             * [ColumnarTranspositionCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/ColumnarTranspositionCipher.java)
@@ -203,6 +204,7 @@
               * [SameTreesCheck](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/SameTreesCheck.java)
               * [SegmentTree](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/SegmentTree.java)
               * [SplayTree](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/SplayTree.java)
+              * [Treap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/Treap.java)
               * [TreeRandomNode](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/TreeRandomNode.java)
               * [TrieImp](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/TrieImp.java)
               * [VerticalOrderTraversal](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/VerticalOrderTraversal.java)
@@ -457,6 +459,7 @@
             * [GenerateSubsets](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/Recursion/GenerateSubsets.java)
           * scheduling
             * [FCFSScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/FCFSScheduling.java)
+            * [MLFQScheduler](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/MLFQScheduler.java)
             * [PreemptivePriorityScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/PreemptivePriorityScheduling.java)
             * [RRScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/RRScheduling.java)
             * [SJFScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/SJFScheduling.java)
@@ -618,6 +621,7 @@
           * ciphers
             * a5
               * [LFSRTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/a5/LFSRTest.java)
+            * [AutokeyTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/AutokeyTest.java)
             * [BlowfishTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/BlowfishTest.java)
             * [CaesarTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/CaesarTest.java)
             * [DESTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/DESTest.java)
@@ -728,6 +732,7 @@
               * [PreOrderTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/PreOrderTraversalTest.java)
               * [SameTreesCheckTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/SameTreesCheckTest.java)
               * [SplayTreeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/SplayTreeTest.java)
+              * [TreapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/TreapTest.java)
               * [TreeTestUtils](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/TreeTestUtils.java)
               * [TrieImpTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/TrieImpTest.java)
               * [VerticalOrderTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/VerticalOrderTraversalTest.java)
@@ -911,6 +916,7 @@
             * [GenerateSubsetsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/Recursion/GenerateSubsetsTest.java)
           * scheduling
             * [FCFSSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/FCFSSchedulingTest.java)
+            * [MLFQSchedulerTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/MLFQSchedulerTest.java)
             * [PreemptivePrioritySchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/PreemptivePrioritySchedulingTest.java)
             * [RRSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/RRSchedulingTest.java)
             * [SJFSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/SJFSchedulingTest.java)

src/main/java/com/thealgorithms/bitmanipulation/CountSetBits.java

@@ -48,4 +48,32 @@ public long countSetBits(long num) {
         }
         return cnt;
     }
+
+    /**
+     * This approach takes O(1) running time to count the set bits, but requires a pre-processing.
+     *
+     * So, we divide our 32-bit input into 8-bit chunks, with four chunks. We have 8 bits in each chunk.
+     *
+     * Then the range is from 0-255 (0 to 2^7).
+     * So, we may need to count set bits from 0 to 255 in individual chunks.
+     *
+     * @param num takes a long number
+     * @return the count of set bits in the binary equivalent
+     */
+    public int lookupApproach(int num) {
+        int[] table = new int[256];
+        table[0] = 0;
+
+        for (int i = 1; i < 256; i++) {
+            table[i] = (i & 1) + table[i >> 1]; // i >> 1 equals to i/2
+        }
+
+        int res = 0;
+        for (int i = 0; i < 4; i++) {
+            res += table[num & 0xff];
+            num >>= 8;
+        }
+
+        return res;
+    }
 }